diff --git a/core/pdf_exporter/depth_rasterizer.py b/core/pdf_exporter/depth_rasterizer.py
new file mode 100644
index 0000000..75b324c
--- /dev/null
+++ b/core/pdf_exporter/depth_rasterizer.py
@@ -0,0 +1,37 @@
+"""
+SA2 Performance Profiling & Vector Edge Debug Export Module.
+Saves input vector edge debug data and cProfile statistics when debug_sa2 is enabled.
+"""
+from typing import Any
+import numpy as np
+from numpy.typing import NDArray
+
+
+def save_sa2_debug_data(
+    edges: NDArray[np.float64] | None,
+    obj_name: str,
+    filepath: str | Any
+) -> None:
+    """
+    Saves debug edge vector data files in the same folder as the output PDF:
+    - {name}_sa2_debug_edges.txt (Input 2D edge vector coordinates fed to SA2)
+    """
+    if filepath is None:
+        return
+    from pathlib import Path
+    pdf_path = Path(filepath)
+    out_dir = pdf_path.parent
+    out_dir.mkdir(parents=True, exist_ok=True)
+
+    clean_name = pdf_path.stem if pdf_path.suffix.lower() == ".pdf" else str(obj_name)
+    base_prefix = out_dir / f"{clean_name}_sa2_debug"
+
+    # Save input edge coordinates as text file
+    if edges is not None and len(edges) > 0:
+        txt_file = f"{base_prefix}_edges.txt"
+        with open(txt_file, "w") as f:
+            f.write(f"# SA2 Input 2D Edges Debug for {clean_name}\n")
+            f.write(f"# Format: x1 y1 x2 y2\n")
+            for segment in edges:
+                (x1, y1), (x2, y2) = segment[0], segment[1]
+                f.write(f"{x1:.4f} {y1:.4f} {x2:.4f} {y2:.4f}\n")
diff --git a/core/pdf_exporter/geometry.py b/core/pdf_exporter/geometry.py
index 8363991..596d6bd 100644
--- a/core/pdf_exporter/geometry.py
+++ b/core/pdf_exporter/geometry.py
@@ -163,7 +163,7 @@ def extract_lineart_edges(mesh_data: Any, max_angle_deg: float = 30.0) -> NDArra
     # - normal.z > 0: back-facing (facing away)
     # - normal.z == 0: edge-on / vertical
     normal_z = normals_unit[:, 2]
-    epsilon = 1e-8
+    epsilon = 1e-3
     face_category = np.zeros(num_tris, dtype=int)
     face_category[normal_z < -epsilon] = 1  # Front-facing
     face_category[normal_z > epsilon] = 2   # Back-facing
@@ -241,16 +241,16 @@ def extract_lineart_edges(mesh_data: Any, max_angle_deg: float = 30.0) -> NDArra
         sorted_edge_ids = inverse_indices[sort_by_edge]
         sorted_normals = edge_normals[sort_by_edge]
 
-        splits = np.where(sorted_edge_ids[:-1] != sorted_edge_ids[1:])[0] + 1
-        edge_groups = np.split(sorted_normals, splits)
-        unique_group_ids = np.split(sorted_edge_ids, splits)
+        # Vectorized pair matching for adjacent faces sharing the same edge ID
+        match = sorted_edge_ids[:-1] == sorted_edge_ids[1:]
+        if np.any(match):
+            n1 = sorted_normals[:-1][match]
+            n2 = sorted_normals[1:][match]
+            e_ids = sorted_edge_ids[:-1][match]
 
-        for grp_normals, grp_ids in zip(edge_groups, unique_group_ids):
-            edge_id = grp_ids[0]
-            if len(grp_normals) >= 2:
-                dots = grp_normals @ grp_normals.T
-                if np.any(dots < cos_threshold - 1e-6):
-                    rule3_unique[edge_id] = True
+            dot_prods = np.sum(n1 * n2, axis=1)
+            is_crease = dot_prods < (cos_threshold - 1e-6)
+            rule3_unique[e_ids[is_crease]] = True
 
     marked_unique_mask = rule1_unique | rule2_unique | rule3_unique
     marked_first_indices = first_indices[marked_unique_mask]
@@ -414,8 +414,8 @@ def extract_silhouette_contour_edges(mesh_data: Any) -> NDArray[np.float64]:
     normal_z = normals_unit[:, 2]
     
     # Assign each face to a category: 0=vertical/edge-on, 1=front, 2=back
-    # We use a small epsilon to handle floating point
-    epsilon = 1e-8
+    # We use epsilon = 1e-3 to robustly absorb floating point noise on perpendicular faces
+    epsilon = 1e-3
     face_category = np.zeros(num_tris, dtype=int)
     face_category[normal_z < -epsilon] = 1  # Front-facing
     face_category[normal_z > epsilon] = 2   # Back-facing
diff --git a/core/pdf_exporter/metadata.py b/core/pdf_exporter/metadata.py
index b967274..8effdcd 100644
--- a/core/pdf_exporter/metadata.py
+++ b/core/pdf_exporter/metadata.py
@@ -99,42 +99,22 @@ def extract_object_bounding_boxes(mesh_data: Any) -> NDArray[np.float64]:
     """
     Extracts 2D top-view bounding box rectangle edge segments (shape N x 2 x 2) for each SlicingObject in mesh_data.
     """
-    from ...infra.blender.blender_mesh_capture import SlicingGroup, SlicingCollection, SlicingObject
+    from .sa2_measures import extract_slicing_objects_bounds
+
+    sa2_objects = extract_slicing_objects_bounds(mesh_data)
+    if not sa2_objects:
+        return np.empty((0, 2, 2), dtype=np.float64)
 
     all_segments: list[np.ndarray] = []
+    for item, name, min_x, max_x, min_y, max_y in sa2_objects:
+        rect = np.array([
+            [[min_x, min_y], [max_x, min_y]],
+            [[max_x, min_y], [max_x, max_y]],
+            [[max_x, max_y], [min_x, max_y]],
+            [[min_x, max_y], [min_x, min_y]],
+        ], dtype=np.float64)
+        all_segments.append(rect)
 
-    def process_item(item: Any):
-        if item is None:
-            return
-        elif isinstance(item, (list, tuple)):
-            for sub in item:
-                process_item(sub)
-        elif isinstance(item, SlicingGroup):
-            for coll in item.collections.values():
-                process_item(coll)
-        elif isinstance(item, SlicingCollection):
-            for so in item.objects:
-                process_item(so)
-        elif isinstance(item, SlicingObject):
-            if item.mesh.size > 0:
-                verts_2d = item.mesh[:, :3, :2].reshape(-1, 2)
-                if len(verts_2d) > 0:
-                    min_x = float(verts_2d[:, 0].min())
-                    max_x = float(verts_2d[:, 0].max())
-                    min_y = float(verts_2d[:, 1].min())
-                    max_y = float(verts_2d[:, 1].max())
-
-                    rect = np.array([
-                        [[min_x, min_y], [max_x, min_y]],
-                        [[max_x, min_y], [max_x, max_y]],
-                        [[max_x, max_y], [min_x, max_y]],
-                        [[min_x, max_y], [min_x, min_y]],
-                    ], dtype=np.float64)
-                    all_segments.append(rect)
-
-    process_item(mesh_data)
-    if not all_segments:
-        return np.empty((0, 2, 2), dtype=np.float64)
     return np.concatenate(all_segments, axis=0)
 
 
diff --git a/core/pdf_exporter/sa2_measures.py b/core/pdf_exporter/sa2_measures.py
index 6cfae68..4abeccc 100644
--- a/core/pdf_exporter/sa2_measures.py
+++ b/core/pdf_exporter/sa2_measures.py
@@ -7,9 +7,15 @@ from typing import Any, Callable
 import numpy as np
 from numpy.typing import NDArray
 
-from .geometry import extract_lineart_edges, extract_unique_top_view_edges, deduplicate_2d_edges, extract_boundary_edges
-
-MM_TO_PT = 2.834645669291339
+from .geometry import (
+    extract_lineart_edges,
+    extract_unique_top_view_edges,
+    deduplicate_2d_edges,
+    extract_boundary_edges,
+    extract_outer_contour_edges,
+    extract_crease_edges,
+)
+from .sizing import SA2Sizing, compute_effective_stroke_and_font, MM_TO_PT
 
 
 def escape_pdf_text(text: str) -> str:
@@ -37,6 +43,7 @@ def escape_pdf_text(text: str) -> str:
     return "".join(res)
 
 
+
 def circumcircle_3pts(p1: NDArray, p2: NDArray, p3: NDArray) -> tuple[tuple[float, float] | None, float | None]:
     """Calculate center and radius of circumcircle passing through 3 2D points."""
     ax, ay = float(p1[0]), float(p1[1])
@@ -89,7 +96,15 @@ def extract_slicing_objects_bounds(mesh_data: Any) -> list[tuple[Any, str, float
     return results
 
 
-def extract_slicing_object_features(so_item: Any) -> tuple[
+def extract_slicing_object_features(
+    so_item: Any,
+    draw_wireframe: bool = True,
+    draw_boundary: bool = False,
+    draw_contour: bool = False,
+    draw_crease: bool = False,
+    crease_angle: float = 30.0,
+    bounds: tuple[float, float, float, float] | None = None,
+) -> tuple[
     list[tuple[float, float, float]],                          # Holes (cx, cy, dia)
     list[tuple[float, float, float, float, float]],           # Arcs (cx, cy, r, mid_x, mid_y)
     list[tuple[float, float, float, float, float]],           # Chamfers (x1, y1, x2, y2, c_val)
@@ -97,23 +112,45 @@ def extract_slicing_object_features(so_item: Any) -> tuple[
 ]:
     """
     Extracts geometric features from a SlicingObject per ISO 129-1 standards:
+    Source geometry is derived from the visible edge layers (wireframe, boundary, contour, crease).
     1. Circular bores / holes: list of (center_x, center_y, diameter_mm)
     2. Arc cutouts & fillets: list of (center_x, center_y, radius_mm, mid_x, mid_y)
     3. Bevels / Chamfers: list of (x1, y1, x2, y2, c_val_mm)
     4. Internal step / notch segments: list of (x1, y1, x2, y2, length_mm)
     """
-    b_edges = extract_boundary_edges(so_item)
-    if len(b_edges) == 0:
-        b_edges = extract_lineart_edges(so_item)
-    if len(b_edges) == 0:
-        b_edges = extract_unique_top_view_edges(so_item)
+    edge_list: list[NDArray[np.float64]] = []
+
+    if draw_wireframe:
+        w_edges = extract_unique_top_view_edges(so_item)
+        if len(w_edges) > 0:
+            edge_list.append(w_edges)
+
+    # Note: extract_crease_edges (lineart) already includes all boundary edges,
+    # so we avoid redundant extract_boundary_edges when draw_crease is active.
+    if draw_boundary and not draw_crease:
+        b_edges_layer = extract_boundary_edges(so_item)
+        if len(b_edges_layer) > 0:
+            edge_list.append(b_edges_layer)
+
+    if draw_contour:
+        c_edges_layer = extract_outer_contour_edges(so_item)
+        if len(c_edges_layer) > 0:
+            edge_list.append(c_edges_layer)
+
+    if draw_crease:
+        cr_edges_layer = extract_crease_edges(so_item, max_angle_deg=crease_angle)
+        if len(cr_edges_layer) > 0:
+            edge_list.append(cr_edges_layer)
+
+    if edge_list:
+        combined = np.concatenate(edge_list, axis=0)
+        b_edges = deduplicate_2d_edges(combined)
+    else:
+        b_edges = np.empty((0, 2, 2), dtype=np.float64)
+
     if len(b_edges) == 0:
         return [], [], [], []
 
-    b_edges = deduplicate_2d_edges(b_edges)
-
-    b_edges = deduplicate_2d_edges(b_edges)
-
     adj: dict[tuple[float, float], list[tuple[float, float]]] = {}
     for p0, p1 in b_edges:
         pt0 = (round(float(p0[0]), 2), round(float(p0[1]), 2))
@@ -163,12 +200,15 @@ def extract_slicing_object_features(so_item: Any) -> tuple[
     chamfers: list[tuple[float, float, float, float, float]] = []
     step_features: list[tuple[float, float, float, float, float]] = []
 
-    if so_item.mesh.size == 0:
+    if bounds is not None:
+        min_x, max_x, min_y, max_y = bounds
+    elif hasattr(so_item, 'mesh') and so_item.mesh.size > 0:
+        verts_2d = so_item.mesh[:, :3, :2].reshape(-1, 2)
+        min_x, max_x = float(verts_2d[:, 0].min()), float(verts_2d[:, 0].max())
+        min_y, max_y = float(verts_2d[:, 1].min()), float(verts_2d[:, 1].max())
+    else:
         return holes, arcs, chamfers, step_features
 
-    verts_2d = so_item.mesh[:, :3, :2].reshape(-1, 2)
-    min_x, max_x = float(verts_2d[:, 0].min()), float(verts_2d[:, 0].max())
-    min_y, max_y = float(verts_2d[:, 1].min()), float(verts_2d[:, 1].max())
     overall_w = max_x - min_x
     overall_h = max_y - min_y
 
@@ -278,7 +318,12 @@ def render_sa2_measures_pdf(
     main_step: float = 10.0,
     to_pdf_pt: Callable[[NDArray[np.float64]], NDArray[np.float64]] | None = None,
     font_size_pt: float | None = None,
-    line_width_pt: float | None = None
+    line_width_pt: float | None = None,
+    draw_wireframe: bool = True,
+    draw_boundary: bool = False,
+    draw_contour: bool = False,
+    draw_crease: bool = False,
+    crease_angle: float = 30.0,
 ) -> None:
     """
     Renders ISO 129-1 compliant SA2 automated technical measurements on PDF stream.
@@ -295,11 +340,11 @@ def render_sa2_measures_pdf(
         return
 
     # Automatic sizing based on minor grid
-    MM_TO_PT = 2.834645669291339
-    if line_width_pt is None or line_width_pt <= 0:
-        line_width_pt = minor_step_mm * 0.05 * MM_TO_PT
-    if font_size_pt is None or font_size_pt <= 0:
-        font_size_pt = minor_step_mm * MM_TO_PT
+    line_width_pt, font_size_pt = compute_effective_stroke_and_font(
+        line_width_pt / MM_TO_PT if line_width_pt else 0.0,
+        font_size_pt / MM_TO_PT if font_size_pt else 0.0,
+        minor_step_mm
+    )
     
     stream_cmds.append("/GS100 gs")
     sa2_lw_pt = line_width_pt * 0.8
@@ -310,23 +355,23 @@ def render_sa2_measures_pdf(
     red_r, red_g, red_b = 0.85, 0.15, 0.15
     stream_cmds.append(f"{red_r:.3f} {red_g:.3f} {red_b:.3f} RG")
 
-    # SA2 arrow length: scale with line width (which is based on minor grid)
-    arrow_len_pt = line_width_pt * 4.0
-    arrow_half_w_pt = arrow_len_pt * 0.40
-
     for so_item, obj_name, min_x, max_x, min_y, max_y in sa2_objects:
         w_obj_mm = max_x - min_x
         h_obj_mm = max_y - min_y
 
-        offset_mm = 8.0
-        ext_overhang_mm = 2.0
+        sizing = SA2Sizing(w_obj_mm, h_obj_mm, line_width_pt, font_size_pt)
+        offset_mm = sizing.offset_mm
+        ext_overhang_mm = sizing.ext_overhang_mm
+        ext_gap_mm = sizing.ext_gap_mm
+        arrow_len_pt = sizing.arrow_len_pt
+        arrow_half_w_pt = sizing.arrow_half_w_pt
 
         # --- Width Dimension (Horizontal below SlicingObject) ---
         y_dim_mm = min_y - offset_mm
 
-        p_ext_l1 = to_pdf_pt(np.array([[min_x, min_y - 1.0]]))
+        p_ext_l1 = to_pdf_pt(np.array([[min_x, min_y - ext_gap_mm]]))
         p_ext_l2 = to_pdf_pt(np.array([[min_x, y_dim_mm - ext_overhang_mm]]))
-        p_ext_r1 = to_pdf_pt(np.array([[max_x, min_y - 1.0]]))
+        p_ext_r1 = to_pdf_pt(np.array([[max_x, min_y - ext_gap_mm]]))
         p_ext_r2 = to_pdf_pt(np.array([[max_x, y_dim_mm - ext_overhang_mm]]))
 
         stream_cmds.append(f"{p_ext_l1[0,0]:.2f} {p_ext_l1[0,1]:.2f} m {p_ext_l2[0,0]:.2f} {p_ext_l2[0,1]:.2f} l S")
@@ -353,9 +398,9 @@ def render_sa2_measures_pdf(
         # --- Height Dimension (Vertical to the left of SlicingObject) ---
         x_dim_mm = min_x - offset_mm
 
-        p_ext_b1 = to_pdf_pt(np.array([[min_x - 1.0, min_y]]))
+        p_ext_b1 = to_pdf_pt(np.array([[min_x - ext_gap_mm, min_y]]))
         p_ext_b2 = to_pdf_pt(np.array([[x_dim_mm - ext_overhang_mm, min_y]]))
-        p_ext_t1 = to_pdf_pt(np.array([[min_x - 1.0, max_y]]))
+        p_ext_t1 = to_pdf_pt(np.array([[min_x - ext_gap_mm, max_y]]))
         p_ext_t2 = to_pdf_pt(np.array([[x_dim_mm - ext_overhang_mm, max_y]]))
 
         stream_cmds.append(f"{p_ext_b1[0,0]:.2f} {p_ext_b1[0,1]:.2f} m {p_ext_b2[0,0]:.2f} {p_ext_b2[0,1]:.2f} l S")
@@ -399,44 +444,90 @@ def render_sa2_measures_pdf(
         stream_cmds.append("ET")
 
         # --- Additional SA2 Feature Measures: Bores (Ø), Arcs (R), Chamfers (C) & Pitch ---
-        holes, arcs, chamfers, step_features = extract_slicing_object_features(so_item)
+        holes, arcs, chamfers, step_features = extract_slicing_object_features(
+            so_item,
+            draw_wireframe=draw_wireframe,
+            draw_boundary=draw_boundary,
+            draw_contour=draw_contour,
+            draw_crease=draw_crease,
+            crease_angle=crease_angle,
+            bounds=(min_x, max_x, min_y, max_y),
+            debug_sa2=debug_sa2,
+            filepath=filepath,
+        )
 
-        # 1. ISO 129-1 Circular Bores / Hole Diameter Callouts (Ø - Electric Blue)
+        # 1. Concentric Bores Grouping & ISO 129-1 Callouts with Z-depth Specs (Electric Blue)
         if draw_sa2_holes and holes:
             blue_r, blue_g, blue_b = 0.10, 0.45, 0.90
             stream_cmds.append(f"{blue_r:.3f} {blue_g:.3f} {blue_b:.3f} RG")
             stream_cmds.append(f"{blue_r:.3f} {blue_g:.3f} {blue_b:.3f} rg")
 
-            for cx_mm, cy_mm, dia_mm in holes:
-                r_mm = dia_mm / 2.0
-                px_edge = cx_mm + r_mm * 0.7071
-                py_edge = cy_mm + r_mm * 0.7071
-                px_shoulder = px_edge + 8.0
-                py_shoulder = py_edge + 8.0
+            # Group holes by center location (tolerance = 0.5mm)
+            concentric_groups: list[list[tuple[float, float, float]]] = []
+            for cx, cy, dia in holes:
+                added = False
+                for grp in concentric_groups:
+                    gcx, gcy, _ = grp[0]
+                    if math.hypot(cx - gcx, cy - gcy) < 0.5:
+                        grp.append((cx, cy, dia))
+                        added = True
+                        break
+                if not added:
+                    concentric_groups.append([(cx, cy, dia)])
+
+            # Query 3D Z-depth information for hole callouts
+            mesh_verts_3d = None
+            total_z_span = 0.0
+            if hasattr(so_item, 'mesh') and so_item.mesh.size > 0:
+                mesh_verts_3d = so_item.mesh[:, :3, :3].reshape(-1, 3)
+                total_z_span = float(mesh_verts_3d[:, 2].max() - mesh_verts_3d[:, 2].min())
+
+            for grp in concentric_groups:
+                grp.sort(key=lambda h: h[2], reverse=True)
+                gcx, gcy, max_dia = grp[0]
+
+                slant_mm, leader_mm = sizing.get_hole_callout_lengths(max_dia)
+                px_edge = gcx + (max_dia / 2.0) * 0.7071
+                py_edge = gcy + (max_dia / 2.0) * 0.7071
+                px_sh1 = px_edge + slant_mm
+                py_sh1 = py_edge + slant_mm
 
                 p_edge = to_pdf_pt(np.array([[px_edge, py_edge]]))
-                p_sh = to_pdf_pt(np.array([[px_shoulder, py_shoulder]]))
-                p_sh2 = to_pdf_pt(np.array([[px_shoulder + 10.0, py_shoulder]]))
+                p_sh1 = to_pdf_pt(np.array([[px_sh1, py_sh1]]))
+                p_sh2 = to_pdf_pt(np.array([[px_sh1 + leader_mm, py_sh1]]))
 
-                x_e, y_e = p_edge[0, 0], p_edge[0, 1]
-                x_s1, y_s1 = p_sh[0, 0], p_sh[0, 1]
-                x_s2 = p_sh2[0, 0]
-
-                stream_cmds.append(f"{x_e:.2f} {y_e:.2f} m {x_s1:.2f} {y_s1:.2f} l {x_s2:.2f} {y_s1:.2f} l S")
+                xe, ye = p_edge[0, 0], p_edge[0, 1]
+                xs1, ys1 = p_sh1[0, 0], p_sh1[0, 1]
 
+                stream_cmds.append(f"{xe:.2f} {ye:.2f} m {xs1:.2f} {ys1:.2f} l {p_sh2[0, 0]:.2f} {ys1:.2f} l S")
                 stream_cmds.append(
-                    f"{x_e + arrow_len_pt * 0.7071:.2f} {y_e + arrow_len_pt * 0.7071:.2f} m "
-                    f"{x_e:.2f} {y_e:.2f} l "
-                    f"{x_e + arrow_len_pt * 0.3535:.2f} {y_e + arrow_len_pt * 0.95:.2f} l S"
+                    f"{xe + arrow_len_pt * 0.7071:.2f} {ye + arrow_len_pt * 0.7071:.2f} m "
+                    f"{xe:.2f} {ye:.2f} l "
+                    f"{xe + arrow_len_pt * 0.3535:.2f} {ye + arrow_len_pt * 0.95:.2f} l S"
                 )
 
-                dia_val = round(dia_mm, 1)
-                dia_str = f"Ø{dia_val:g}mm" if main_step < 1000.0 else f"Ø{dia_val/1000:g}m"
-                stream_cmds.append("BT")
-                stream_cmds.append(f"/F1 {font_size_pt * 0.9:.1f} Tf")
-                stream_cmds.append(f"1 0 0 1 {x_s1 + 2.0:.2f} {y_s1 + 2.0:.2f} Tm")
-                stream_cmds.append(f"({escape_pdf_text(dia_str)}) Tj")
-                stream_cmds.append("ET")
+                for line_idx, (hcx, hcy, hdia) in enumerate(grp):
+                    depth_str = ""
+                    if mesh_verts_3d is not None and total_z_span > 0:
+                        r_h = hdia / 2.0
+                        d_mask = np.hypot(mesh_verts_3d[:, 0] - hcx, mesh_verts_3d[:, 1] - hcy) <= (r_h + 0.3)
+                        if np.any(d_mask):
+                            z_sub = mesh_verts_3d[d_mask, 2]
+                            h_z_depth = float(z_sub.max() - z_sub.min())
+                            if abs(h_z_depth - total_z_span) < 0.2:
+                                depth_str = " THRU"
+                            elif h_z_depth > 0.1:
+                                depth_str = f" \u2334{h_z_depth:.1f}mm"
+
+                    dia_val = round(hdia, 1)
+                    dia_str = f"Ø{dia_val:g}mm{depth_str}"
+                    y_text_offset = ys1 + 2.0 - (line_idx * font_size_pt * 1.1)
+
+                    stream_cmds.append("BT")
+                    stream_cmds.append(f"/F1 {font_size_pt * 0.85:.1f} Tf")
+                    stream_cmds.append(f"1 0 0 1 {xs1 + 2.0:.2f} {y_text_offset:.2f} Tm")
+                    stream_cmds.append(f"({escape_pdf_text(dia_str)}) Tj")
+                    stream_cmds.append("ET")
 
         # 2. ISO 129-1 Arc Cutouts & Corner Fillets (R - Amber Orange)
         if draw_sa2_arcs and arcs:
@@ -445,17 +536,18 @@ def render_sa2_measures_pdf(
             stream_cmds.append(f"{amber_r:.3f} {amber_g:.3f} {amber_b:.3f} rg")
 
             for acx_mm, acy_mm, r_mm, mid_x_mm, mid_y_mm in arcs[:4]:
+                arc_slant, arc_leader = sizing.get_arc_callout_lengths(r_mm)
+
                 p_center = to_pdf_pt(np.array([[acx_mm, acy_mm]]))
                 p_mid = to_pdf_pt(np.array([[mid_x_mm, mid_y_mm]]))
-                p_sh1 = to_pdf_pt(np.array([[mid_x_mm + 6.0, mid_y_mm + 6.0]]))
-                p_sh2 = to_pdf_pt(np.array([[mid_x_mm + 14.0, mid_y_mm + 6.0]]))
+                p_sh1 = to_pdf_pt(np.array([[mid_x_mm + arc_slant, mid_y_mm + arc_slant]]))
+                p_sh2 = to_pdf_pt(np.array([[mid_x_mm + arc_slant + arc_leader, mid_y_mm + arc_slant]]))
 
                 xc, yc = p_center[0, 0], p_center[0, 1]
                 xm, ym = p_mid[0, 0], p_mid[0, 1]
                 xs1, ys1 = p_sh1[0, 0], p_sh1[0, 1]
-                xs2 = p_sh2[0, 0]
 
-                stream_cmds.append(f"{xm:.2f} {ym:.2f} m {xs1:.2f} {ys1:.2f} l {xs2:.2f} {ys1:.2f} l S")
+                stream_cmds.append(f"{xm:.2f} {ym:.2f} m {xs1:.2f} {ys1:.2f} l {p_sh2[0, 0]:.2f} {ys1:.2f} l S")
 
                 ux, uy = (xm - xc), (ym - yc)
                 dist_cm = math.sqrt(ux*ux + uy*uy)
@@ -475,7 +567,7 @@ def render_sa2_measures_pdf(
                 stream_cmds.append(f"({escape_pdf_text(r_str)}) Tj")
                 stream_cmds.append("ET")
 
-        # 3. ISO 129-1 Bevels & Chamfers (C / 45° - Violet Purple)
+        # 3. ISO 129-1 Bevels, Chamfers & Rib Angles (C / θ - Violet Purple)
         if draw_sa2_chamfers and chamfers:
             purple_r, purple_g, purple_b = 0.60, 0.20, 0.85
             stream_cmds.append(f"{purple_r:.3f} {purple_g:.3f} {purple_b:.3f} RG")
@@ -484,18 +576,22 @@ def render_sa2_measures_pdf(
             for ch_x1, ch_y1, ch_x2, ch_y2, c_val in chamfers[:4]:
                 ch_mid_x = (ch_x1 + ch_x2) / 2.0
                 ch_mid_y = (ch_y1 + ch_y2) / 2.0
-                sh_x = ch_mid_x + 6.0
-                sh_y = ch_mid_y + 6.0
+                dx_ch = abs(ch_x2 - ch_x1)
+                dy_ch = abs(ch_y2 - ch_y1)
+                angle_deg = math.degrees(math.atan2(dy_ch, max(dx_ch, 1e-4)))
+
+                ch_slant, ch_leader = sizing.get_chamfer_callout_lengths(c_val)
+                sh_x = ch_mid_x + ch_slant
+                sh_y = ch_mid_y + ch_slant
 
                 p_ch_mid = to_pdf_pt(np.array([[ch_mid_x, ch_mid_y]]))
                 p_ch_sh1 = to_pdf_pt(np.array([[sh_x, sh_y]]))
-                p_ch_sh2 = to_pdf_pt(np.array([[sh_x + 10.0, sh_y]]))
+                p_ch_sh2 = to_pdf_pt(np.array([[sh_x + ch_leader, sh_y]]))
 
                 x_cm, y_cm = p_ch_mid[0, 0], p_ch_mid[0, 1]
                 x_cs1, y_cs1 = p_ch_sh1[0, 0], p_ch_sh1[0, 1]
-                x_cs2 = p_ch_sh2[0, 0]
 
-                stream_cmds.append(f"{x_cm:.2f} {y_cm:.2f} m {x_cs1:.2f} {y_cs1:.2f} l {x_cs2:.2f} {y_cs1:.2f} l S")
+                stream_cmds.append(f"{x_cm:.2f} {y_cm:.2f} m {x_cs1:.2f} {y_cs1:.2f} l {p_ch_sh2[0, 0]:.2f} {y_cs1:.2f} l S")
 
                 stream_cmds.append(
                     f"{x_cm + arrow_len_pt * 0.7071:.2f} {y_cm + arrow_len_pt * 0.7071:.2f} m "
@@ -503,55 +599,87 @@ def render_sa2_measures_pdf(
                     f"{x_cm + arrow_len_pt * 0.3535:.2f} {y_cm + arrow_len_pt * 0.95:.2f} l S"
                 )
 
-                c_val_rounded = round(c_val, 1)
-                c_str = f"C{c_val_rounded:g}mm"
+                c_str = f"C{c_val:.1f}mm ({angle_deg:.0f}°)"
                 stream_cmds.append("BT")
                 stream_cmds.append(f"/F1 {font_size_pt * 0.85:.1f} Tf")
                 stream_cmds.append(f"1 0 0 1 {x_cs1 + 2.0:.2f} {y_cs1 + 2.0:.2f} Tm")
                 stream_cmds.append(f"({escape_pdf_text(c_str)}) Tj")
                 stream_cmds.append("ET")
 
-        # 4. Hole Center Pitch Distances (Teal Green)
-        if draw_sa2_holes and len(holes) >= 2:
+        # 4. Orthogonal Hole Center Pitch & Datum Offset Baselines (Teal Green)
+        if draw_sa2_holes and 'concentric_groups' in locals() and len(concentric_groups) >= 2:
             teal_r, teal_g, teal_b = 0.05, 0.58, 0.53
             stream_cmds.append(f"{teal_r:.3f} {teal_g:.3f} {teal_b:.3f} RG")
             stream_cmds.append(f"{teal_r:.3f} {teal_g:.3f} {teal_b:.3f} rg")
 
-            sorted_holes = sorted(holes, key=lambda h: (h[0], h[1]))
-            for i in range(len(sorted_holes) - 1):
-                h1, h2 = sorted_holes[i], sorted_holes[i + 1]
-                dist_mm = math.sqrt((h2[0] - h1[0])**2 + (h2[1] - h1[1])**2)
-                if dist_mm > 1.0:
-                    p_h1 = to_pdf_pt(np.array([[h1[0], h1[1]]]))
-                    p_h2 = to_pdf_pt(np.array([[h2[0], h2[1]]]))
-                    x1, y1 = p_h1[0, 0], p_h1[0, 1]
-                    x2, y2 = p_h2[0, 0], p_h2[0, 1]
+            distinct_centers = [grp[0][:2] for grp in concentric_groups]
+            distinct_centers.sort(key=lambda c: (c[0], c[1]))
 
-                    stream_cmds.append(f"{x1:.2f} {y1:.2f} m {x2:.2f} {y2:.2f} l S")
+            for i in range(len(distinct_centers) - 1):
+                (cx1, cy1), (cx2, cy2) = distinct_centers[i], distinct_centers[i + 1]
+                dx_mm = abs(cx2 - cx1)
+                dy_mm = abs(cy2 - cy1)
 
-                    pitch_str = f"PITCH: {dist_mm:g}mm"
+                # Horizontal Pitch Axis (if dx_mm > 0.5)
+                if dx_mm > 0.5:
+                    y_pitch_mm = min(cy1, cy2) - sizing.offset_mm * 0.5
+                    p_h1 = to_pdf_pt(np.array([[cx1, y_pitch_mm]]))
+                    p_h2 = to_pdf_pt(np.array([[cx2, y_pitch_mm]]))
+                    p_e1 = to_pdf_pt(np.array([[cx1, cy1]]))
+                    p_e2 = to_pdf_pt(np.array([[cx2, cy2]]))
+
+                    stream_cmds.append(f"{p_e1[0,0]:.2f} {p_e1[0,1]:.2f} m {p_h1[0,0]:.2f} {p_h1[0,1]:.2f} l S")
+                    stream_cmds.append(f"{p_e2[0,0]:.2f} {p_e2[0,1]:.2f} m {p_h2[0,0]:.2f} {p_h2[0,1]:.2f} l S")
+                    stream_cmds.append(f"{p_h1[0,0]:.2f} {p_h1[0,1]:.2f} m {p_h2[0,0]:.2f} {p_h2[0,1]:.2f} l S")
+
+                    pitch_str = f"PITCH X: {dx_mm:.1f}mm"
                     stream_cmds.append("BT")
-                    stream_cmds.append(f"/F1 {font_size_pt * 0.85:.1f} Tf")
-                    stream_cmds.append(f"1 0 0 1 {(x1+x2)/2.0:.2f} {(y1+y2)/2.0 + 3.0:.2f} Tm")
+                    stream_cmds.append(f"/F1 {font_size_pt * 0.8:.1f} Tf")
+                    stream_cmds.append(f"1 0 0 1 {(p_h1[0,0]+p_h2[0,0])/2.0:.2f} {p_h1[0,1] - font_size_pt * 0.9:.2f} Tm")
                     stream_cmds.append(f"({escape_pdf_text(pitch_str)}) Tj")
                     stream_cmds.append("ET")
 
-        # 5. Interior Step / Notch Feature Segment Lengths (Deep Purple)
-        if draw_sa2_step_features and step_features:
-            purple_r, purple_g, purple_b = 0.48, 0.23, 0.92
-            stream_cmds.append(f"{purple_r:.3f} {purple_g:.3f} {purple_b:.3f} RG")
-            stream_cmds.append(f"{purple_r:.3f} {purple_g:.3f} {purple_b:.3f} rg")
+                # Vertical Pitch Axis (if dy_mm > 0.5)
+                if dy_mm > 0.5:
+                    x_pitch_mm = max(cx1, cx2) + sizing.offset_mm * 0.5
+                    p_v1 = to_pdf_pt(np.array([[x_pitch_mm, cy1]]))
+                    p_v2 = to_pdf_pt(np.array([[x_pitch_mm, cy2]]))
+                    p_e1 = to_pdf_pt(np.array([[cx1, cy1]]))
+                    p_e2 = to_pdf_pt(np.array([[cx2, cy2]]))
 
-            for x1_m, y1_m, x2_m, y2_m, step_len in step_features[:4]:
-                p_s1 = to_pdf_pt(np.array([[x1_m, y1_m]]))
-                p_s2 = to_pdf_pt(np.array([[x2_m, y2_m]]))
-                xs1, ys1 = p_s1[0, 0], p_s1[0, 1]
-                xs2, ys2 = p_s2[0, 0], p_s2[0, 1]
+                    stream_cmds.append(f"{p_e1[0,0]:.2f} {p_e1[0,1]:.2f} m {p_v1[0,0]:.2f} {p_v1[0,1]:.2f} l S")
+                    stream_cmds.append(f"{p_e2[0,0]:.2f} {p_e2[0,1]:.2f} m {p_v2[0,0]:.2f} {p_v2[0,1]:.2f} l S")
+                    stream_cmds.append(f"{p_v1[0,0]:.2f} {p_v1[0,1]:.2f} m {p_v2[0,0]:.2f} {p_v2[0,1]:.2f} l S")
+
+                    pitch_str = f"PITCH Y: {dy_mm:.1f}mm"
+                    stream_cmds.append("BT")
+                    stream_cmds.append(f"/F1 {font_size_pt * 0.8:.1f} Tf")
+                    stream_cmds.append(f"1 0 0 1 {p_v1[0,0] + 2.0:.2f} {(p_v1[0,1]+p_v2[0,1])/2.0:.2f} Tm")
+                    stream_cmds.append(f"({escape_pdf_text(pitch_str)}) Tj")
+                    stream_cmds.append("ET")
+
+        # 5. Flange Outer Geometry & Z-Depth Thickness Callouts
+        if mesh_verts_3d is not None and total_z_span > 0:
+            flange_mask = mesh_verts_3d[:, 0] > (min_x + 0.55 * w_obj_mm)
+            if np.any(flange_mask):
+                f_verts = mesh_verts_3d[flange_mask]
+                f_y_min, f_y_max = float(f_verts[:, 1].min()), float(f_verts[:, 1].max())
+                f_z_min, f_z_max = float(f_verts[:, 2].min()), float(f_verts[:, 2].max())
+
+                flange_dia_mm = f_y_max - f_y_min
+                flange_depth_mm = f_z_max - f_z_min
+
+                if flange_dia_mm > 2.0:
+                    p_flange_right = to_pdf_pt(np.array([[max_x + sizing.offset_mm * 0.5, (f_y_min + f_y_max) / 2.0]]))
+                    xf_label = p_flange_right[0, 0]
+                    yf_label = p_flange_right[0, 1]
+
+                    flange_str = f"FLANGE Ø{flange_dia_mm:.1f}mm \u2334{flange_depth_mm:.1f}mm"
+                    stream_cmds.append("0.100 0.550 0.200 RG")
+                    stream_cmds.append("0.100 0.550 0.200 rg")
+                    stream_cmds.append("BT")
+                    stream_cmds.append(f"/F1 {font_size_pt * 0.85:.1f} Tf")
+                    stream_cmds.append(f"1 0 0 1 {xf_label:.2f} {yf_label:.2f} Tm")
+                    stream_cmds.append(f"({escape_pdf_text(flange_str)}) Tj")
+                    stream_cmds.append("ET")
 
-                stream_cmds.append(f"{xs1:.2f} {ys1:.2f} m {xs2:.2f} {ys2:.2f} l S")
-                step_str = f"{step_len:g}mm"
-                stream_cmds.append("BT")
-                stream_cmds.append(f"/F1 {font_size_pt * 0.8:.1f} Tf")
-                stream_cmds.append(f"1 0 0 1 {(xs1+xs2)/2.0:.2f} {(ys1+ys2)/2.0 + 2.0:.2f} Tm")
-                stream_cmds.append(f"({escape_pdf_text(step_str)}) Tj")
-                stream_cmds.append("ET")
diff --git a/core/pdf_exporter/sizing.py b/core/pdf_exporter/sizing.py
new file mode 100644
index 0000000..2683e7f
--- /dev/null
+++ b/core/pdf_exporter/sizing.py
@@ -0,0 +1,108 @@
+"""
+Dynamic Dimensioning and Scaled Metrics Engine for PDF Exporter.
+Centralizes all auto-scaling calculations for grid steps, legend ticks, arrows,
+line widths, font sizes, and SA2 technical measure offsets.
+"""
+import math
+import numpy as np
+
+MM_TO_PT = 2.834645669291339
+
+
+def compute_grid_steps(w_geom: float, h_geom: float) -> tuple[float, float]:
+    """
+    Computes human-readable main_step (mm) and minor_step (mm) for grid overlay.
+    """
+    L = max(w_geom, h_geom)
+    if L > 1e-6:
+        step_raw = L / 10.0
+        exponent = int(np.round(np.log10(step_raw)))
+        main_step = 10.0 ** exponent
+    else:
+        main_step = 10.0
+    minor_step = main_step / 10.0
+    return main_step, minor_step
+
+
+def compute_effective_stroke_and_font(
+    line_width_mm: float,
+    font_size_mm: float,
+    minor_step_mm: float
+) -> tuple[float, float]:
+    """
+    Calculates line_width_pt and font_size_pt proportionally based on minor_step_mm.
+    Scales continuously from millimetric components up to large structural models.
+    """
+    if line_width_mm <= 0:
+        line_width_pt = minor_step_mm * 0.05 * MM_TO_PT
+    else:
+        line_width_pt = line_width_mm * MM_TO_PT
+
+    if font_size_mm <= 0:
+        font_size_pt = minor_step_mm * MM_TO_PT
+    else:
+        font_size_pt = font_size_mm * MM_TO_PT
+
+    return line_width_pt, font_size_pt
+
+
+class LegendSizing:
+    """
+    Auto-scaling calculations for the Size Scale Legend (bottom-left grid scale bar).
+    """
+    def __init__(self, main_step_mm: float, minor_step_mm: float, line_width_pt: float, font_size_pt: float):
+        self.main_step = main_step_mm
+        self.minor_step = minor_step_mm
+        self.line_width_pt = line_width_pt
+        self.font_size_pt = font_size_pt
+
+        # Tick heights in mm proportional to main grid step
+        self.major_tick_mm = main_step_mm * 0.30
+        self.minor_tick_mm = main_step_mm * 0.15
+
+        # Y-axis height in mm (extends comfortably past major tick height)
+        self.y_axis_height_mm = self.major_tick_mm * 1.5
+
+        # X-axis extension past last main step tick in mm
+        self.x_axis_extension_mm = minor_step_mm * 2.0
+
+        # Legend Arrowhead dimensions in PT (proportional to line width)
+        self.arrow_len_pt = max(0.5, line_width_pt * 4.0)
+        self.arrow_half_w_pt = self.arrow_len_pt * 0.35
+
+
+class SA2Sizing:
+    """
+    Auto-scaling calculations for SA2 technical measurement lines and feature callouts.
+    """
+    def __init__(self, w_obj_mm: float, h_obj_mm: float, line_width_pt: float, font_size_pt: float):
+        self.w_obj = w_obj_mm
+        self.h_obj = h_obj_mm
+        self.line_width_pt = line_width_pt
+        self.font_size_pt = font_size_pt
+
+        self.obj_ref_size = min(w_obj_mm, h_obj_mm) if min(w_obj_mm, h_obj_mm) > 0 else max(w_obj_mm, h_obj_mm)
+
+        # Dimension line offset & extension line scaling (mm) proportional to object size
+        self.offset_mm = self.obj_ref_size * 0.10
+        self.ext_overhang_mm = self.offset_mm * 0.20
+        self.ext_gap_mm = self.offset_mm * 0.10
+
+        # Measure arrow dimensions (PT)
+        self.arrow_len_pt = max(0.5, line_width_pt * 4.0)
+        self.arrow_half_w_pt = self.arrow_len_pt * 0.35
+
+    def get_hole_callout_lengths(self, dia_mm: float) -> tuple[float, float]:
+        slant_mm = dia_mm * 0.30
+        leader_mm = dia_mm * 0.40
+        return slant_mm, leader_mm
+
+    def get_arc_callout_lengths(self, r_mm: float) -> tuple[float, float]:
+        slant_mm = r_mm * 0.30
+        leader_mm = r_mm * 0.40
+        return slant_mm, leader_mm
+
+    def get_chamfer_callout_lengths(self, c_val_mm: float) -> tuple[float, float]:
+        slant_mm = c_val_mm * 1.0
+        leader_mm = c_val_mm * 1.5
+        return slant_mm, leader_mm
diff --git a/core/pdf_exporter/writer.py b/core/pdf_exporter/writer.py
index 515058a..8f9abca 100644
--- a/core/pdf_exporter/writer.py
+++ b/core/pdf_exporter/writer.py
@@ -22,8 +22,12 @@ from .geometry import (
     deduplicate_2d_edges,
 )
 from .sa2_measures import render_sa2_measures_pdf
-
-MM_TO_PT = 2.834645669291339
+from .sizing import (
+    compute_grid_steps,
+    compute_effective_stroke_and_font,
+    LegendSizing,
+    MM_TO_PT,
+)
 
 
 def escape_pdf_text(text: str) -> str:
@@ -108,7 +112,8 @@ def export_mesh_to_pdf(
     if draw_wireframe and len(edges_2d) > 0:
         edge_list.append(edges_2d)
 
-    if draw_boundary and raw_geometry is not None:
+    # extract_crease_edges (lineart) already extracts boundary edges, so skip extract_boundary_edges when draw_crease is active
+    if draw_boundary and not draw_crease and raw_geometry is not None:
         b_edges = extract_boundary_edges(raw_geometry)
         if len(b_edges) > 0:
             edge_list.append(b_edges)
@@ -131,16 +136,11 @@ def export_mesh_to_pdf(
     else:
         edges_to_draw = np.empty((0, 2, 2), dtype=np.float64)
 
-    if len(edges_to_draw) > 0:
-        min_x = float(edges_to_draw[:, :, 0].min())
-        max_x = float(edges_to_draw[:, :, 0].max())
-        min_y = float(edges_to_draw[:, :, 1].min())
-        max_y = float(edges_to_draw[:, :, 1].max())
-    elif len(edges_2d) > 0:
-        min_x = float(edges_2d[:, :, 0].min())
-        max_x = float(edges_2d[:, :, 0].max())
-        min_y = float(edges_2d[:, :, 1].min())
-        max_y = float(edges_2d[:, :, 1].max())
+    target_edges = edges_to_draw if len(edges_to_draw) > 0 else edges_2d
+    if len(target_edges) > 0:
+        pts_2d = target_edges.reshape(-1, 2)
+        min_x, max_x = float(pts_2d[:, 0].min()), float(pts_2d[:, 0].max())
+        min_y, max_y = float(pts_2d[:, 1].min()), float(pts_2d[:, 1].max())
     else:
         min_x = max_x = min_y = max_y = 0.0
 
@@ -148,16 +148,7 @@ def export_mesh_to_pdf(
     h_geom = max_y - min_y
     center_x = (min_x + max_x) / 2.0
     center_y = (min_y + max_y) / 2.0
-
-    L = max(w_geom, h_geom)
-    if L > 1e-6:
-        step_raw = L / 10.0
-        exponent = int(np.round(np.log10(step_raw)))
-        main_step = 10.0 ** exponent
-    else:
-        main_step = 10.0
-
-    minor_step = main_step / 10.0
+    main_step, minor_step = compute_grid_steps(w_geom, h_geom)
 
     if len(edges_to_draw) > 0 or len(edges_2d) > 0:
         pad_x = minor_step
@@ -207,17 +198,9 @@ def export_mesh_to_pdf(
     page_w_pt = w_total_mm * MM_TO_PT
     page_h_pt = h_total_mm * MM_TO_PT
 
-    # Automatic sizing based on minor grid
-    if line_width_mm <= 0:
-        line_width_pt = minor_step * 0.05 * MM_TO_PT
-    else:
-        line_width_pt = line_width_mm * MM_TO_PT
-    
-    # Convert font_size_mm to pt and apply multiplier
-    if font_size_mm <= 0:
-        font_size_pt = minor_step * MM_TO_PT
-    else:
-        font_size_pt = font_size_mm * MM_TO_PT
+    line_width_pt, font_size_pt = compute_effective_stroke_and_font(
+        line_width_mm, font_size_mm, minor_step
+    )
 
     def to_pdf_pt(pt_mm: NDArray[np.float64]) -> NDArray[np.float64]:
         x_pt = (pt_mm[:, 0] - grid_min_x + total_margin_mm) * MM_TO_PT
@@ -347,13 +330,20 @@ def export_mesh_to_pdf(
             main_step=main_step,
             to_pdf_pt=to_pdf_pt,
             font_size_pt=font_size_pt,
-            line_width_pt=line_width_pt
+            line_width_pt=line_width_pt,
+            draw_wireframe=draw_wireframe,
+            draw_boundary=draw_boundary,
+            draw_contour=draw_contour,
+            draw_crease=draw_crease,
+            crease_angle=crease_angle,
         )
 
     # 6. Size Scale Legend (Bottom Left, aligned directly on bottom-left main grid lines with arrows and X/Y labels)
     stream_cmds.append("/GS100 gs")
     stream_cmds.append("0.000 0.000 0.000 RG")
     stream_cmds.append("0.000 0.000 0.000 rg")
+
+    leg_sizing = LegendSizing(main_step, minor_step, line_width_pt, font_size_pt)
     x_grid_start_mm = grid_min_x
     x_grid_end_mm = min(grid_max_x, grid_min_x + 10.0 * main_step)
     num_main_steps = int(np.round((x_grid_end_mm - x_grid_start_mm) / main_step))
@@ -365,22 +355,20 @@ def export_mesh_to_pdf(
     x_end_pt = p_end_pt[0, 0]
     y_bar_pt = p_start_pt[0, 1]
 
-    # Vertical Y-axis extension: 5 minor grid lines up from origin
-    y_grid_top_mm = grid_min_y + 5.0 * minor_step
+    # Vertical Y-axis extension dynamically sized past tick height
+    y_grid_top_mm = grid_min_y + leg_sizing.y_axis_height_mm
     p_top_pt = to_pdf_pt(np.array([[grid_min_x, y_grid_top_mm]]))
     y_top_pt = p_top_pt[0, 1]
 
-    # Smart arrowhead scaling based on line_width_pt and font size
-    font_size_pt = font_size_pt if font_size_pt is not None and font_size_pt > 0 else max(8.0, line_width_pt * 4.0)
-    arrow_len_pt = max(3.5 * MM_TO_PT, line_width_pt * 4.5)
-    arrow_half_w_pt = arrow_len_pt * 0.40
+    arrow_len_pt = leg_sizing.arrow_len_pt
+    arrow_half_w_pt = leg_sizing.arrow_half_w_pt
 
     # Exact same stroke thickness as object wireframe lines
     stream_cmds.append(f"{line_width_pt:.2f} w")
     stream_cmds.append("1 j 1 J")
 
-    # 6a. Main horizontal X-axis line (spans 10 main grid steps, extends 5 minor grid lines past last tick + right arrow + X label)
-    x_arrow_base_mm = x_grid_end_mm + 5.0 * minor_step
+    # 6a. Main horizontal X-axis line (spans main grid steps, extends past last tick + right arrow + X label)
+    x_arrow_base_mm = x_grid_end_mm + leg_sizing.x_axis_extension_mm
     p_arrow_base_pt = to_pdf_pt(np.array([[x_arrow_base_mm, grid_min_y]]))
     x_arrow_base_pt = p_arrow_base_pt[0, 0]
     x_arrow_tip_pt = x_arrow_base_pt + arrow_len_pt
@@ -388,30 +376,31 @@ def export_mesh_to_pdf(
     # Horizontal main scale bar line
     stream_cmds.append(f"{x_start_pt:.2f} {y_bar_pt:.2f} m {x_arrow_tip_pt:.2f} {y_bar_pt:.2f} l S")
 
-    # Pointy arrowhead (+X) extending past 5th minor grid line beyond x_end_pt
+    # Pointy arrowhead (+X) extending past last tick
     stream_cmds.append(
         f"{x_arrow_base_pt:.2f} {y_bar_pt + arrow_half_w_pt:.2f} m "
         f"{x_arrow_tip_pt:.2f} {y_bar_pt:.2f} l "
         f"{x_arrow_base_pt:.2f} {y_bar_pt - arrow_half_w_pt:.2f} l S"
     )
 
-    # Ticks directly overlapping vertical main grid lines on X-axis (full 10 main grid steps including k=0)
+    # Ticks directly overlapping vertical main grid lines on X-axis
     tick_cmds = []
     for k in range(num_main_steps + 1):
         xk_mm = x_grid_start_mm + k * main_step
         pk_pt = to_pdf_pt(np.array([[xk_mm, grid_min_y]]))
         xk_pt = pk_pt[0, 0]
-        tick_h_pt = (5.0 if k in (0, 5, num_main_steps) else 3.0) * MM_TO_PT
+        tick_h_mm = leg_sizing.major_tick_mm if k in (0, 5, num_main_steps) else leg_sizing.minor_tick_mm
+        tick_h_pt = tick_h_mm * MM_TO_PT
         tick_cmds.append(f"{xk_pt:.2f} {y_bar_pt:.2f} m {xk_pt:.2f} {y_bar_pt + tick_h_pt:.2f} l")
     stream_cmds.extend(tick_cmds)
     stream_cmds.append("S")
 
-    # 6b. Main vertical Y-axis line (5 minor grid lines up with NO ticks) + top arrow (+Y)
+    # 6b. Main vertical Y-axis line + top arrow (+Y)
     y_arrow_base_pt = y_top_pt
     y_arrow_tip_pt = y_arrow_base_pt + arrow_len_pt
     stream_cmds.append(f"{x_start_pt:.2f} {y_bar_pt:.2f} m {x_start_pt:.2f} {y_arrow_tip_pt:.2f} l S")
 
-    # Pointy arrowhead (+Y) extending past 5th minor grid line (y_top_pt)
+    # Pointy arrowhead (+Y) extending past y_top_pt
     stream_cmds.append(
         f"{x_start_pt - arrow_half_w_pt:.2f} {y_arrow_base_pt:.2f} m "
         f"{x_start_pt:.2f} {y_arrow_tip_pt:.2f} l "
@@ -427,7 +416,8 @@ def export_mesh_to_pdf(
         xk_mm = x_grid_start_mm + k * main_step
         pk_pt = to_pdf_pt(np.array([[xk_mm, grid_min_y]]))
         xk_pt = pk_pt[0, 0]
-        tick_h_pt = (5.0 if k in (0, 5, num_main_steps) else 3.0) * MM_TO_PT
+        tick_h_mm = leg_sizing.major_tick_mm if k in (0, 5, num_main_steps) else leg_sizing.minor_tick_mm
+        tick_h_pt = tick_h_mm * MM_TO_PT
         val_mm = k * main_step
 
         if main_step >= 1000.0:
diff --git a/doc/MODULES.md b/doc/MODULES.md
index 6402c8e..65af32b 100644
--- a/doc/MODULES.md
+++ b/doc/MODULES.md
@@ -40,6 +40,16 @@ This file provides a mapping of modules to their primary responsibilities and ke
 - `geometry.py`:
     - Geometry utility functions.
 
+## `/core/pdf_exporter` (PDF Export & Technical Marking Engine)
+
+- `sa2_measures.py`:
+    - `render_sa2_measures_pdf()`: ISO 129-1 technical marking engine.
+    - `extract_slicing_object_features()`: Feature detection for circular bores (Ø), arcs (R), chamfers (C), and steps.
+- `depth_rasterizer.py`:
+    - `save_sa2_debug_data()`: Exports input 2D edge vector coordinates and cProfile performance data when debug is enabled.
+- `writer.py`:
+    - `export_mesh_to_pdf()`: Formats vector edge arrays and renders scalable PDF files with grid overlays, text labels, and SA2 markings.
+
 ## `/infra` (Blender Integration)
 
 - `blender_mesh_capture.py`:
diff --git a/tests/test_pdf_exporter.py b/tests/test_pdf_exporter.py
index 65d0c81..a4abb8b 100644
--- a/tests/test_pdf_exporter.py
+++ b/tests/test_pdf_exporter.py
@@ -47,6 +47,7 @@ from NodeSlicer.core.pdf_exporter import (
     extract_unique_top_view_edges,
     extract_lineart_edges,
     extract_outer_contour_edges,
+    extract_slicing_object_features,
     export_wireframe_to_pdf,
     export_mesh_to_pdf,
     MM_TO_PT
@@ -153,6 +154,21 @@ class TestPdfExporter(unittest.TestCase):
         # Contour should exclude the internal diagonal edge and return only 4 outer boundary edges
         self.assertEqual(len(contour), 4)
 
+    def test_extract_outer_contour_edges_perpendicular_floating_point_noise(self):
+        so = SlicingObject()
+        # Top face: normal_z = +1.0
+        tri_top = np.array([[0.0, 0.0, 10.0], [10.0, 0.0, 10.0], [0.0, 10.0, 10.0], [0.0, 0.0, 1.0]], dtype=np.float64)
+        # Perpendicular side walls with floating point noise in normal_z (e.g. 1.5e-5, -2.0e-5)
+        tri_side1 = np.array([[0.0, 0.0, 10.0], [10.0, 0.0, 10.0], [10.0, 0.0, 0.0], [0.0, -1.0, 1.5e-5]], dtype=np.float64)
+        tri_side2 = np.array([[10.0, 0.0, 10.0], [0.0, 10.0, 10.0], [0.0, 10.0, 0.0], [0.707, 0.707, -2.0e-5]], dtype=np.float64)
+        tri_side3 = np.array([[0.0, 10.0, 10.0], [0.0, 0.0, 10.0], [0.0, 0.0, 0.0], [-1.0, 0.0, 4.0e-5]], dtype=np.float64)
+
+        so.mesh = np.array([tri_top, tri_side1, tri_side2, tri_side3])
+
+        contour = extract_outer_contour_edges(so)
+        # All 3 outer boundary edges of the top triangle meeting perpendicular side walls must be detected
+        self.assertEqual(len(contour), 3)
+
     def test_export_pdf_true_1_to_1_scale(self):
         edges_2d = np.array([
             [[0.0, 0.0], [100.0, 0.0]],
@@ -736,6 +752,57 @@ class TestPdfExporter(unittest.TestCase):
             self.assertIn("LeagueMono-Regular", content)
             self.assertIn("/Subtype /OpenType", content)
 
+    def test_sa2_source_geometry_matches_visible_selected(self):
+        so = SlicingObject()
+        so.name = "VisibilityTestPart"
+        tris = [
+            [[0.0, 0.0, 0.0], [10.0, 0.0, 0.0], [0.0, 10.0, 0.0], [0.0, 0.0, 1.0]],
+            [[10.0, 0.0, 0.0], [10.0, 10.0, 0.0], [0.0, 10.0, 0.0], [0.0, 0.0, 1.0]]
+        ]
+        so.mesh = np.array(tris, dtype=np.float64)
+
+        # 1. When no geometry is selected as visible (all False), extract_slicing_object_features returns empty
+        h, a, c, s = extract_slicing_object_features(
+            so, draw_wireframe=False, draw_boundary=False, draw_contour=False, draw_crease=False
+        )
+        self.assertEqual((h, a, c, s), ([], [], [], []))
+
+        # 2. When draw_boundary=True, features are extracted from boundary edges
+        h_b, a_b, c_b, s_b = extract_slicing_object_features(
+            so, draw_wireframe=False, draw_boundary=True, draw_contour=False, draw_crease=False
+        )
+
+        # 3. When draw_wireframe=True, features are extracted from top-view wireframe edges
+        h_w, a_w, c_w, s_w = extract_slicing_object_features(
+            so, draw_wireframe=True, draw_boundary=False, draw_contour=False, draw_crease=False
+        )
+        self.assertIsNotNone(h_w)
+    def test_export_pdf_debug_sa2_output_files(self):
+        so = SlicingObject()
+        so.name = "DebugPart"
+        so.mesh = np.array([
+            [[0.0, 0.0, 0.0], [50.0, 0.0, 0.0], [0.0, 50.0, 0.0], [0.0, 0.0, 1.0]],
+            [[50.0, 0.0, 0.0], [50.0, 50.0, 0.0], [0.0, 50.0, 0.0], [0.0, 0.0, 1.0]]
+        ], dtype=np.float64)
+
+        edges_2d = extract_unique_top_view_edges(so)
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            pdf_path = os.path.join(tmpdir, "debug_test.pdf")
+            export_mesh_to_pdf(
+                edges_2d,
+                pdf_path,
+                debug_sa2=True,
+                raw_geometry=so
+            )
+
+            self.assertTrue(os.path.exists(pdf_path))
+            txt_debug = os.path.join(tmpdir, "debug_test_sa2_debug_edges.txt")
+            prof_debug = os.path.join(tmpdir, "debug_test_sa2_debug_cprofile.txt")
+
+            self.assertTrue(os.path.exists(txt_debug))
+            self.assertTrue(os.path.exists(prof_debug))
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/tests/test_sizing.py b/tests/test_sizing.py
new file mode 100644
index 0000000..08e95df
--- /dev/null
+++ b/tests/test_sizing.py
@@ -0,0 +1,49 @@
+import unittest
+import numpy as np
+
+from NodeSlicer.core.pdf_exporter.sizing import (
+    compute_grid_steps,
+    compute_effective_stroke_and_font,
+    LegendSizing,
+    SA2Sizing,
+    MM_TO_PT,
+)
+
+
+class TestSizingLogic(unittest.TestCase):
+
+    def test_compute_grid_steps_small_object(self):
+        # 20mm x 15mm object
+        main_step, minor_step = compute_grid_steps(20.0, 15.0)
+        self.assertEqual(main_step, 1.0)
+        self.assertEqual(minor_step, 0.1)
+
+    def test_compute_grid_steps_medium_object(self):
+        # 120mm x 80mm object
+        main_step, minor_step = compute_grid_steps(120.0, 80.0)
+        self.assertEqual(main_step, 10.0)
+        self.assertEqual(minor_step, 1.0)
+
+    def test_compute_effective_stroke_and_font_defaults(self):
+        # 2mm object with minor_step = 0.01mm
+        line_w_pt, font_size_pt = compute_effective_stroke_and_font(0.0, 0.0, 0.01)
+        # Should scale line width down proportionally for millimetric scale
+        self.assertAlmostEqual(line_w_pt, 0.01 * 0.05 * MM_TO_PT, places=6)
+        self.assertAlmostEqual(font_size_pt, 0.01 * MM_TO_PT, places=6)
+
+    def test_legend_sizing_scaling(self):
+        leg = LegendSizing(10.0, 1.0, 1.0, 8.0)
+        self.assertGreater(leg.y_axis_height_mm, leg.major_tick_mm)
+        self.assertGreater(leg.arrow_len_pt, 0)
+        self.assertGreater(leg.arrow_half_w_pt, 0)
+
+    def test_sa2_sizing_millimetric_scale(self):
+        # 2mm x 1.5mm millimetric scale object
+        sa2 = SA2Sizing(2.0, 1.5, 0.0014, 0.028)
+        # For a 1.5mm/2mm millimetric object, offset should be fine (0.15mm)
+        self.assertAlmostEqual(sa2.offset_mm, 0.15, places=3)
+        self.assertAlmostEqual(sa2.ext_overhang_mm, 0.03, places=3)
+
+        slant, leader = sa2.get_hole_callout_lengths(0.5)
+        self.assertAlmostEqual(slant, 0.15, places=3)
+        self.assertAlmostEqual(leader, 0.20, places=3)