Compare PDF
Render two PDFs side by side page by page to spot visual differences.
Compare PDF shows two PDFs side by side, page by page, and highlights the visual differences, so a revised contract or a re-exported report can be checked against the earlier version without reading every line.
Compare PDF shows two documents side by side and highlights where they differ. It is a visual, pixel-based comparison that is good for spotting changes between two versions. Compare PDF is one of UnboundPDF's 53 free browser-based PDF and image tools: it runs on your own device with no upload, no account and no watermark, and reports what it measured on the output.
How to compare PDF — steps & common uses
What people use Compare PDF for
People checking what changed between two versions of a document — a revised contract, an edited draft, a new revision.
- Spot changes between contract drafts
- Compare two document revisions
- Check an edited version against the original
- Find differences page by page
How to compare PDF
- Add PDF A and PDF B; both are rendered on your device and never uploaded.
- Page through the documents using the previous and next buttons.
- Click Show differences to overlay the changed pixels in red.
- Download the difference image for any page you want to keep.
Questions about Compare PDF 6
Are my files uploaded to a server?
No. UnboundPDF processes PDFs locally in the browser — documents are not uploaded to a server. We have no backend that receives, stores, or scans your files.
Is this a text comparison or a visual one?
It is a visual, pixel-by-pixel comparison. It highlights anywhere the two pages look different, rather than diffing the underlying text word by word.
What do the red areas mean?
Red marks the pixels that changed between PDF A and PDF B on that page, and a percentage shows how much of the page differs.
How does it show the differences?
It renders both files and highlights where the pages differ visually, so changes stand out page by page.
Does it compare the wording or the appearance?
It compares how the pages look, which catches moved, added or removed content — including in scans that have no text layer.
Do both files need the same number of pages?
They compare best when aligned, but you can still step through and see where they diverge if the lengths differ.
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How your files are handled
The work runs on your own device, inside the browser tab — so there is no server to send your document to.
- Nothing is uploaded. We have no backend that receives or stores documents, so we cannot see your files during processing or after.
- Your device does the work. Large documents are handled in stages, pages are rendered as you reach them, and each job is checked against your device before it starts — so a long run takes longer on a phone than on a laptop, nothing is queued behind other people's jobs, and you can stop a run at any point without touching your original file.
- No account and no watermark. The output is a clean file you can use anywhere, with no sign-up and no hourly cap.
More optimize tools
Other free PDF utilities that work the same way — in your browser, no sign-up.