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How to Compare Two PDFs and See What Changed

Updated July 13, 2026

Someone sends back a “revised” contract or report, and now you need to know exactly what changed without reading both versions line by line. A visual comparison makes edits, moved text, and added content jump out immediately.

Steps

  1. Add the original PDF, then the changed PDF.
  2. Click Compare.
  3. Download the difference images — one per page, with changes marked in red.

How the comparison works

Rather than comparing text (which can miss layout shifts, image changes, or formatting edits), this tool renders both files to images and compares them pixel by pixel. Anywhere the two versions differ, that area is painted red over a faded copy of the original page — so you get a visual map of exactly what moved, was added, or was removed, including changes a text-only diff would miss entirely.

When page counts don’t match

If one version has more pages than the other — a section was added or cut — the extra pages are compared against a blank page and show up as fully changed. Nothing errors out; you just see those pages flagged as different in their entirety, which is usually exactly what you want to know.

Notes

Both files are rendered and compared entirely in your browser — nothing is uploaded, which matters when you’re diffing confidential drafts or contracts. The output is a set of highlighted images for review, not an automatically merged document; to actually reorganize or extract pages after reviewing the differences, use Organize PDF.

Tools in this guide

Frequently asked questions

How does this actually detect what changed?
Each page of both files is rendered to an image and compared pixel by pixel. Any pixel that differs between the two versions is painted red over a faint grayscale copy of the original, so changes are immediately visible.
Does it work if the two PDFs have a different number of pages?
Yes. Extra pages in the longer file are compared against a blank page, so pages that were added or removed show up as fully changed rather than causing an error.
Does this produce an edited PDF, or something else?
It produces difference images — one per page, with changes highlighted in red — rather than an edited PDF. It's built for spotting and reviewing changes, not for merging them.