PDF Handling

PDF File Handling Rules

Conversion Procedure

• When reading PDF files, always follow this procedure:
  1. Convert the required pages to PNG images using pdftoppm
  2. Analyze the converted images to extract text
• Never include a PDF file directly in an API request body

Prerequisite

• poppler must be installed
  • macOS: brew install poppler
  • openSUSE Tumbleweed: sudo zypper install poppler-tools
  • Ubuntu (LTS): sudo apt install poppler-utils
  • Windows: choco install poppler or scoop install poppler

Page Range Strategy

• Read table of contents pages first to understand structure
• Convert only the pages needed for the current task, not the entire document
• For large PDFs (100+ pages), work in batches of 10-20 pages

Temporary File Management

• Use /tmp/ for converted PNG images
• Use descriptive prefixes for output files (e.g., pdftoppm -png -f 1 -l 5 input.pdf /tmp/project_toc)
• Clean up temporary PNG files after extraction is complete using rm /tmp/<prefix>*.png

Large PDF Handling

• If the Read tool fails due to file size, always fall back to pdftoppm
• Estimate the PDF page offset by comparing displayed page numbers with actual PDF page numbers
• When searching for specific content, use the table of contents to calculate target page numbers rather than scanning sequentially

Command Reference

pdftoppm

# Convert specific page range to PNG
pdftoppm -png -f <first> -l <last> input.pdf /tmp/output_prefix

# Example: convert pages 1-5
pdftoppm -png -f 1 -l 5 input.pdf /tmp/project_toc

# Higher resolution (default 150 DPI, use 300 for small text)
pdftoppm -png -r 300 -f 1 -l 1 input.pdf /tmp/high_res

pdfinfo

# Check page count, file size, and metadata
pdfinfo input.pdf

pdftotext

# Extract text from specific pages (preserve layout)
pdftotext -f 1 -l 5 -layout input.pdf /tmp/output.txt

# Extract all text
pdftotext input.pdf /tmp/output.txt

Workflow

Standard PDF Analysis Procedure

1. Run pdfinfo to check document metadata (page count, size)
2. Convert table of contents pages with pdftoppm to understand structure
3. Selectively convert only the pages needed for the task
4. Analyze images or extract text with pdftotext
5. Clean up temporary files in /tmp/

Page Number Offset Handling

The actual PDF page number and the printed page number in the document may differ.

Library and Tool References

See references/pdf-libraries.md for detailed comparison of PDF libraries (Apache PDFBox, iText, pdf.js, pypdf, pdfplumber, and others) including licensing, capabilities, and selection guide. See references/pdf-text-extraction.md for text/table extraction techniques (Camelot, Tabula, pdfplumber) and OCR guide with Tesseract.

Anti-Patterns

• Converting the entire PDF at once (memory/disk exhaustion on large files)
• Not cleaning up temporary PNG files after extraction
• Converting pages without verifying the page number offset
• Using image conversion when direct text extraction (pdftotext) is sufficient

Related Skills

• error-handling: Error handling patterns for PDF parsing failures
• logging: Logging PDF processing workflows
• testing: Testing strategies for PDF processing logic