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Compare PDFs

docs/tools/compare-pdfs.md

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Compare PDFs

Upload two PDFs and see exactly what changed between them. The tool pairs pages intelligently, detects differences in text, images, annotations, headers, and formatting, and presents them in a side-by-side or overlay view.

How It Works

  1. Upload two PDF files -- the original (left) and the revised version (right).
  2. The tool pairs pages between the documents using content signatures.
  3. Select a view mode: Side by Side or Overlay.
  4. Navigate between page pairs using the pagination controls.
  5. Differences are highlighted and categorized. Use the filter panel to focus on specific change types.
  6. Optionally export the comparison as a PDF report.

Features

  • Automatic page pairing based on content similarity
  • Side-by-side and overlay comparison views
  • Change categorization: text, image, header/footer, annotation, formatting, background
  • Per-category filter toggles to show or hide specific change types
  • Text change search with query filtering
  • OCR support for comparing scanned documents
  • Zoom controls for detailed inspection
  • Synchronized scrolling between panels in side-by-side mode
  • Export comparison results as a PDF

Options

OptionDescription
View ModeSide by Side or Overlay
OCREnable/disable OCR for scanned document comparison
OCR LanguageLanguage for OCR text extraction
Category FiltersToggle visibility of text, image, header/footer, annotation, formatting, and background changes
Change ScopeIn overlay mode, filter between all changes or content-only
ZoomAdjust magnification level for detailed inspection

Use Cases

  • Reviewing contract revisions to find exactly what changed between versions
  • Comparing design mockups to verify that PDF exports match expectations
  • Auditing document changes in regulated industries where every edit must be tracked
  • Verifying that a PDF conversion process preserved the original content accurately
  • Checking translation documents against the source for layout changes

Tips

  • The overlay view stacks both documents on top of each other, making spatial differences (shifted elements, resized images) immediately visible.
  • Enable OCR when comparing scanned documents that do not have a text layer. The comparison engine will extract text from page images.
  • Use category filters to focus on what matters. For example, hide formatting changes when you only care about text content differences.