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Compare PDF
Compare PDF extracts the text of two documents and runs a line-by-line diff, showing exactly which sentences were added, removed or changed. It is built for reviewing contract revisions or checking that two exports really say the same thing.
How to use Compare PDF
- Add the two PDF versions — the older file first, the newer one second.
- Run the comparison; both text layers are extracted page by page.
- Read the diff output, which marks added and removed lines, and copy it for your review notes.
Where Compare PDF is useful
- Checking what a counterparty changed in a returned contract.
- Confirming that a re-export from a design tool kept all the copy.
- Diffing two policy versions before publishing an update.
Formats, algorithms and limits
The comparison works on extracted text, not on rendered pixels: formatting, fonts and image changes are invisible to it. That makes it fast and precise for wording changes, but a visual check is still needed for layout-only edits.
Troubleshooting and honest limits
- Compare the text layer only — if a document is a scan, run it through a text-extraction step first.
- Expect noise from re-flowed text: a paragraph that moved to the next page appears as a change even if the words are identical.
- Use the copied diff in your review notes as evidence of exactly what changed.
Frequently asked questions
Does the comparison detect image or layout changes?
No. It diffs the text layer, so a swapped logo or a margin shift will not appear. Use it for wording, and open both files side by side for visual checks.
What order should I upload the two files in?
Original first, revision second. Added text is then shown as an addition relative to your original document, which matches how review workflows read a diff.
How much of each document is compared?
Every page of both files is extracted, so the diff covers the complete text of both documents rather than a sample.
Can I compare a PDF with a Word file?
Not in one pass. Convert the Word file to PDF first, then compare the two PDFs so both sides produce a text layer.
Related tools
Page written and reviewed by the FreeConvertio engineering team on 2026-10-14. Compare PDF runs entirely in your browser — no uploads, no account and no daily limits.