How do I compare two versions of a PDF and see what changed?
Upload both PDFs to Sealique: their text is compared page by page on the server and the differences shown side by side in your browser, added and removed words highlighted.
The counterparty sent version 3 of the contract and says only the dates changed. Before anyone signs, the comparison shows every line that differs between the two files, page by page, so the claim can be checked in a minute instead of being read twice.
Compare two PDFs now Create an account Verify a signed document
Key facts
- Compare PDF on Sealique puts two versions of a document side by side and highlights every line that was added, removed or changed, included with a Sealique account.
- The comparison is text-based: the words of each page are extracted on the server and compared; layout, images and colours are not compared.
- Changed lines are broken down word by word, so a single altered figure in a clause stands out.
- Up to 120 pages per document; scanned PDFs need OCR first because a picture has no text to compare.
- Only the report is kept with the job; the two PDFs are not added to your library by the comparison.
How is the comparison made?
On Sealique servers the text of every page of both files is extracted line by line. Each page pair is aligned with a sequence comparison that finds the longest common runs, so unchanged lines are matched and the rest is classified as added, removed or replaced. Replaced lines are split into words and compared again, which produces the word-level highlights in the report.
Compare before signing, verify after
The comparison answers what changed between drafts. Once a version is sealed with a PAdES digital signature, the question becomes whether the file changed since, and that is what online verification by verification ID or QR code answers.
Compare PDF, step by step
Open Compare PDF
Sign in, open PDF tools and choose Compare PDF.
Choose the two versions
Drop the older PDF on the left and the newer one on the right, or pick them from your library (up to 50 MB and 120 pages each).
Compare
Press Compare. The text of each page is extracted and compared on the server.
Read the report
Added lines are marked on the right, removed lines on the left, changed lines on both sides with the differing words highlighted. Totals are shown at the top.
Compare PDF is included with a Sealique account; the processing happens in your browser and on our servers, nothing is shared with third parties.
What Compare PDF includes
- Side-by-side, page by page
- Added, removed and changed lines highlighted
- Word-level marks inside changed lines
- Totals per document
- Text-based; works with OCR for scans
- Works from a phone or a computer
Questions people ask
Does it compare the layout or the pictures?
No. The comparison is text-based: it reports differences in the words of each page, not in fonts, positions, colours or images.
A moved paragraph shows as removed on one side and added on the other.
Can I compare scanned documents?
Only after OCR: run OCR PDF on both scans so they carry text, then compare the searchable copies.
What if the page counts differ?
Pages are compared by position; extra pages at the end appear as entirely added or removed.
Are the files stored?
The comparison keeps only the report with the job; the PDFs you uploaded for it are not saved as documents unless they already were in your library.
Does it cost anything?
No. It is included with a Sealique account: no card and no limit on the number of comparisons.