Compare PDF Files
See what changed between two PDF versions.
Compare two PDF versions, review page pairing and inspect visual highlights alongside their selectable text. Up to 20 MB and 40 pages per file. Both documents stay on this device.
Small changes may fall below the comparison resolution or sensitivity. Scans are compared as pictures without OCR. This does not verify signatures, attachments, hidden content or every PDF object.
Review page pictures and text side by side
Choose an original PDF and a revised copy to inspect changes in wording, pictures, page layout and visible page size. Each result shows both page numbers, a difference image and the extracted text. Red marks detected pixel differences; it does not measure the importance or meaning of an edit.
Automatic page pairing uses unchanged page pictures as anchors, then pairs the remaining pages in order. This can help when a page was inserted or deleted. Repeated pages, moved sections and edits around an insertion can be ambiguous. Check the pair list, switch to page-number matching, or use Split PDF and Organize PDF to prepare corresponding sections.
Strict sensitivity includes faint visual differences; the less-sensitive setting ignores more small colour changes. Scanning noise, skew, shifted text and font rendering may produce large highlighted areas. Images are compared at a bounded resolution, so tiny changes can be missed. No detected change does not mean the files are identical in every respect.
Selectable text is compared with whitespace differences ignored. Scans are compared visually without recognizing their words; use OCR PDF first if you also need text. Closed comments, attachments, bookmarks, hidden layers and digital-signature validity are outside this comparison. Download the ZIP for an HTML report, JSON details and page images, then extract it before opening report.html.
Best for: People reviewing revisions of their reports, handouts, proofs and scanned documents before sharing them.
How to use Compare PDF
- Choose the original and revised PDFs, or try the sample with a text edit and an inserted page.
- Choose page pairing and visual sensitivity, then compare. Check the suggested page pairs and use full image size for closer inspection.
- Review the red highlights and extracted text. Download the report ZIP, extract it and open report.html to keep the comparison.
Frequently asked questions
What changes can this PDF comparison show?
It compares rendered page pictures, visible page sizes and selectable text. This can show changed words, pictures, colours or placement. It does not inspect every PDF object, signature, attachment or hidden item.
How are added and removed pages identified?
Automatic mode matches unchanged page pictures in order. Remaining pages are paired in order between those matches, with extra pages labelled added or removed. Moved or repeated pages can be ambiguous, so review every suggested pair.
Can I compare scanned PDFs?
Yes, as page pictures. Scan noise, rotation and slight shifts can create many highlights. The tool does not align or clean up scans automatically. OCR PDF can add selectable text before you compare, but recognition must be checked.
Does no detected change mean the PDFs are identical?
No. Fine differences can fall below the rendering resolution or chosen sensitivity. Text whitespace is ignored. Metadata, attachments, hidden content and signatures are not checked. Use the original files for a full review.
Can I change sensitivity or inspect small details?
Choose Strict to include faint colour differences, Standard for a balanced starting point, or Less sensitive to ignore more faint noise. Full image size lets you scroll around the rendered picture; it does not add detail beyond the comparison resolution.
What is in the downloadable report?
The ZIP contains an HTML report, original and revised page pictures, red difference images and a JSON summary with extracted text. Extract the ZIP, then open report.html. The report contains document content, so share it as carefully as the original PDFs.
Is this a legal redline or signature check?
No. It is a visual and text review aid, not tracked changes, certificate verification or an exhaustive document audit. It does not modify either source file or decide which differences matter.
Are my documents uploaded?
No conversion upload is made. Both PDFs are processed in the browser without an account. Use unlocked files up to 20 MB and 40 pages each. Very large images or dense text may require comparing smaller sections.