diff --git a/bin/md_to_pdf.py b/bin/md_to_pdf.py
new file mode 100644
index 0000000..9a0c913
--- /dev/null
+++ b/bin/md_to_pdf.py
@@ -0,0 +1,115 @@
+"""Markdown to PDF conversion core logic."""
+
+import re
+import uuid
+from pathlib import Path
+
+import click
+
+from bin import templates_registry
+from bin.utils import run_command
+
+
+def md_to_typ(inputs: list[Path]) -> str:
+    """Convert Markdown files to Typst via pandoc."""
+    md_content = ""
+    for inp in inputs:
+        with open(inp, "r", encoding="utf-8") as f:
+            md_content += f.read() + "\n\n"
+    result = run_command(
+        ["pandoc", "-f", "markdown-citations", "-t", "typst", "-"],
+        input=md_content,
+        capture_output=True,
+        text=True,
+    )
+    typ = result.stdout
+    # Pandoc outputs #horizontalrule which Typst does not define
+    typ = typ.replace("#horizontalrule", "#line(length: 100%)")
+    # Remove Pandoc auto-generated heading labels to avoid named-destination
+    # links that break with non-ASCII characters in some PDF readers.
+    typ = re.sub(r"(^=+ .*?)\n<[^>\n]+>\n", r"\1\n", typ, flags=re.MULTILINE)
+    return typ
+
+
+def expand_bookmarks(pdf_path: Path, max_level: int) -> None:
+    """Expand PDF outline nodes up to ``max_level`` without rebuilding."""
+    if max_level <= 1:
+        return
+
+    from pypdf import PdfReader, PdfWriter
+    from pypdf.generic import NumberObject
+
+    reader = PdfReader(str(pdf_path))
+    writer = PdfWriter()
+    writer.clone_document_from_reader(reader)
+
+    outline_root = reader.trailer["/Root"].get("/Outlines")
+    if not outline_root:
+        writer.write(str(pdf_path))
+        return
+
+    def update_count(item_ref, depth=0):
+        item = item_ref.get_object()
+        count = item.get("/Count")
+        if count is not None and depth < max_level:
+            val = int(count)
+            if val < 0:
+                item.update({"/Count": NumberObject(-val)})
+        first = item.get("/First")
+        if first:
+            child = first
+            while child:
+                update_count(child, depth=depth + 1)
+                child = child.get_object().get("/Next")
+
+    first = outline_root.get("/First")
+    if first:
+        update_count(first, depth=0)
+
+    writer.write(str(pdf_path))
+
+
+def build_pdf(
+    template: str,
+    inputs: list[Path],
+    output: Path,
+    bookmark_depth: int = 1,
+) -> None:
+    """Build PDF from Markdown using Typst.
+
+    ``bookmark_depth`` controls outline expansion: ``1`` keeps only top-level
+    bookmarks visible (default), ``2`` expands to second level, and so on.
+    """
+    templates_dir = templates_registry.get_md_to_pdf_root()
+    template_file = templates_dir / template / "template.typ"
+    if not template_file.exists():
+        click.secho(f"Template not found: {template_file}", fg="red", err=True)
+        raise SystemExit(1)
+
+    typ_body = md_to_typ(inputs)
+
+    # Convert pandoc tables to three-line tables
+    typ_body = typ_body.replace("#table(", "#three-line-table(")
+
+    tmp_name = f".{uuid.uuid4().hex}.typ"
+    tmp_path = templates_dir / tmp_name
+    rel_template = f"{template}/template.typ"
+
+    with open(tmp_path, "w", encoding="utf-8") as f:
+        f.write(f'#import "{rel_template}": {template}, three-line-table\n\n')
+        f.write(f"#show: {template}.with()\n\n")
+        f.write(typ_body)
+
+    output = output.resolve()
+    output.parent.mkdir(parents=True, exist_ok=True)
+
+    try:
+        run_command(
+            ["typst", "compile", "--root", "/", tmp_name, str(output)],
+            cwd=str(templates_dir),
+        )
+    finally:
+        tmp_path.unlink(missing_ok=True)
+
+    if output.exists() and bookmark_depth > 1:
+        expand_bookmarks(output, bookmark_depth)