Compare PDFs

See what changed between two PDFs.

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Compare PDFs help

Compare two PDFs to review what changed. Use the available comparison views to inspect differences before accepting a revision or sending a final document.

How to use Compare PDFs

  1. Choose the original as PDF A and the revision as PDF B.
  2. Set Match pages to Automatically or By page number, then select Compare PDFs.
  3. Read Changes summary and inspect the marked differences beside both pages.
  4. Select Download summary to keep a text record, and manually check important differences.
Options explained
Choose PDF A and Choose PDF B
Select the original and revised documents; both are needed for a comparison.
Match pages
Automatically tries to align related pages; By page number compares equal page positions when page order is stable.
Matched pages
Choose a pair to inspect its visible and text differences instead of relying only on the summary.
Limits and supported files

PDF documents. An opening password is required when the file needs one to be read.

Local tests used synthetic 10, 50, 100 and 200 MB PDFs containing large images. Chromium, Firefox and WebKit: completed 10, 50, 100, 200 MB.

Chromium: completed 50 text pages; 300, 1000 text pages did not complete. Firefox: completed 50, 300 text pages; 1000 text pages did not complete. WebKit: completed 50, 300 text pages; 1000 text pages did not complete. Comparison tests used two identical documents with automatic page matching.

Compare PDF was tested on a 16 GB Mac with Chromium, Firefox and WebKit. “Did not complete” includes input limits, errors and test timeouts; try a smaller selection. These are observed examples, not guaranteed limits on your device. WebKit tests do not replace a check in Safari on your own device. The 90-second test window is not a hard limit; some jobs may need longer.

Questions

Does a highlighted difference always mean the meaning changed?

No. A changed font, image or page position can produce a visible difference even when the words mean the same thing. Read the surrounding content before deciding whether a revision is important.

Can comparison replace proofreading?

No. Use the results as a guide and check important names, numbers, dates and missing pages yourself. Scans and complex layouts can need closer visual review than ordinary selectable text.

Which PDF should I choose as the original?

Choose PDF A for the original and PDF B for the revised version, then inspect the differences against both sources.

Can I compare PDFs when pages have moved?

Automatically tries to align related pages; By page number compares equal page positions when page order is stable.

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