PDF Chapter Splitting

Split PDF documents into individual chapter files based on table of contents or text pattern detection.

Overview

This skill handles PDF splitting when:

• A book or document needs to be divided by chapters
• The PDF has embedded bookmarks/outlines, OR
• Chapter boundaries can be detected from text patterns (e.g., "Chapter 1:", "Part One")

Prerequisites

Install pypdf via uv inline script dependency:

# /// script
# dependencies = ["pypdf"]
# ///

Workflow

Phase 1: Analyze PDF Structure

Run scripts/extract_toc.py to analyze the PDF:

uv run ~/.claude/skills/pdf-split/scripts/extract_toc.py <pdf_path>

Output includes:

• Total page count
• Embedded bookmarks/outline (if present)
• Detected chapter patterns from text

Phase 2: Define Chapter Boundaries

Based on Phase 1 output, define chapter boundaries as a list of tuples:

chapters = [
    (start_page, end_page, "chapter_name"),
    # ...
]

If bookmarks exist: Use bookmark page numbers directly.

If no bookmarks:

1. Search for chapter heading patterns in text
2. Verify boundaries by checking page content
3. Present proposed boundaries for user confirmation

Phase 3: Execute Split

Run scripts/split_by_chapters.py with the chapter definitions:

uv run ~/.claude/skills/pdf-split/scripts/split_by_chapters.py <pdf_path> <output_dir> --chapters '<json_chapters>'

Example:

uv run ~/.claude/skills/pdf-split/scripts/split_by_chapters.py \
  ~/book.pdf \
  ~/book_chapters \
  --chapters '[[1,22,"00_Intro"],[23,45,"01_Chapter1"]]'

Common Chapter Patterns

Pattern	Regex	Example
Numbered	Chapter\s+\d+	"Chapter 1", "Chapter 12"
Part + Chapter	Part\s+\w+.*Chapter	"Part One: Chapter 1"
Section	Section\s+\d+	"Section 1.1"
Roman numerals	Chapter\s+[IVXLC]+	"Chapter IV"

Edge Cases

Large Chapter Detection (100+ pages)

When a detected chapter exceeds 100 pages, verify the boundary:

• Check if appendix content is included
• Look for sub-sections that should be separate files

Missing TOC

When no bookmarks or clear patterns exist:

1. Extract first 20 pages of text
2. Look for manual TOC listing
3. Parse page numbers from TOC text

Duplicate Pattern Matches

Filter results to keep only actual chapter starts:

• Chapter headings typically appear at page top
• Ignore references to chapters in body text (e.g., "see Chapter 3")

Output Structure

output_dir/
├── 00_Front_Matter.pdf
├── 01_Chapter_Name.pdf
├── 02_Chapter_Name.pdf
├── ...
└── Appendix.pdf

Naming convention: {index:02d}_{sanitized_name}.pdf

Integration Notes

For NotebookLM Upload

Split PDFs are suitable for NotebookLM sources:

• Each chapter as separate source enables targeted queries
• Recommended: Keep files under 500KB when possible
• Large chapters may need further splitting

For RAG Systems

Chapter-level splitting provides natural semantic boundaries for:

• Document chunking
• Retrieval granularity
• Citation accuracy

Scripts Reference

Script	Purpose
scripts/extract_toc.py	Analyze PDF, extract bookmarks and detect chapter patterns
scripts/split_by_chapters.py	Execute split with provided chapter definitions

Additional Resources

• references/pypdf-guide.md - pypdf API quick reference for custom operations