How to Compare Two PDFs and See What Changed (Contract Revisions)
Lawyers redline contracts. Editors track manuscript changes. Auditors compare year-over-year reports. Spotting differences between two PDF versions by eye is unreliable above a few pages. Here's how to run a real diff in your browser, free.
The problem
Counsel sends you "the revised version." You don't have time to read all 40 pages again — you want to see exactly what changed. Adobe Acrobat Pro's Compare Files works at $20/month. Free online diff tools usually upload both PDFs to their servers, which is a non-starter for sealed motions, NDAs, or confidential drafts.
Use the tool now
Open the compare pdfs tool and follow the steps below.
Step-by-step
- 1
Open the Compare PDFs tool
Drop both PDFs into [Compare PDFs](/en/tools/compare-pdfs). Original on the left, revised on the right. Both stay in your browser.
- 2
Wait for the diff to render
The tool walks each page side-by-side, highlighting added text in green, deleted text in red, and modified text in yellow. Multi-page diffs take a few seconds.
- 3
Review changes by category
Filter to "Insertions only" to see new clauses, "Deletions only" to see removed language, or "All changes" for the full picture.
- 4
Export a redline
Download the comparison as a single PDF with both versions side-by-side and changes highlighted — useful for emailing back to opposing counsel or board members.
Pro tips
- •For large contracts (50+ pages), focus on operative sections (definitions, indemnification, term/termination) where wording changes matter most.
- •OCR scanned PDFs first — image-based PDFs can't be diff'd at the text level, only visually.
- •For collaborative editing across many revisions, consider using a redline plugin in Word and exporting to PDF after each round, rather than diffing PDFs after the fact.
- •When the diff finds zero changes but the file size differs, the only differences are formatting/metadata — not substantive.
Frequently asked questions
Can it detect text moved within the document?
Yes — moved paragraphs are flagged as both an insertion (at the new location) and a deletion (at the old location). The redline export marks them with a "moved" annotation.
What about formatting-only changes (font, color, size)?
Detected and listed separately from content changes. Useful when reviewing brand-compliance edits or accessibility rewrites.
Does this work on Acrobat Pro's Compare-formatted PDFs?
Yes — those are standard PDFs with annotation layers, fully diff-compatible.
Privacy: what if I'm comparing sealed court filings?
PDFShed processes both files in your browser via WebAssembly. They're never uploaded. Verifiable in DevTools — no POST requests for your files.