When reviewing document revisions — contracts, reports, proposals — being able to see exactly what changed between version 1 and version 2 saves hours of manual review. Here is how to compare PDF versions with a free visual diff tool.
Go to pdfeditor.onl/compare-pdf. No sign-up or installation required. The comparison engine runs entirely in your browser — neither PDF is sent to a server.
Upload the original PDF (Version 1) and the revised PDF (Version 2). The tool accepts any two PDFs, even if they have different page counts.
Tip: For the clearest diff, make sure both PDFs have the same page size and layout orientation. A layout change will show up as a large diff even if the text is the same.
Click Compare. The tool renders both PDFs as images and performs a pixel-level diff. Changed areas are highlighted in red on a grayscale background — making them immediately obvious.
Navigate through the comparison pages. The diff view shows: red highlights = changed pixels (added or removed content). Unchanged areas appear in grayscale. The change percentage for each page is shown.
Click Download All Pages as PDF to export a complete comparison report. This is useful for audits, legal review, or sharing the diff summary with a team.
Yes. The tool compares pages by position — page 1 vs page 1, page 2 vs page 2, etc. If the versions have different numbers of pages, the extra pages in the longer document are flagged as entirely new/changed.
The comparison is pixel-based, not text-based. Any visual difference — a single comma, a moved image, a font change — is detected. For text-specific diffing, copy both PDFs to Word and use Word's compare feature.
Pixel differences above a threshold of ~15 luminance units are highlighted. Minor JPEG compression artifacts between versions may trigger false positives — for best results, compare PDFs created from the same software source.