Compare two PDFs
Compare PDF puts two versions of the same document side by side, page by page, and paints over the areas whose appearance changed. It is what you want for checking a contract revision, seeing what the client altered in a proposal, or confirming the final version is the one that was approved. All processing runs in your browser.
Three steps, nothing to install.
The whole job happens on your computer, start to finish.
Choose the two files
Drag both PDFs into the tool window. The first is the reference version, the second is the one being compared.
See the differences on screen
The first pages show up side by side straight away, with the differing areas marked on both sides.
Download the report
Get a PDF with every compared page, one sheet per page, with the differences painted over.
Does it compare the text or the image?
The image. The tool draws both pages and measures where the pixels diverge. It does not read words, and it cannot tell a sentence from a logo: it knows that area of the sheet stopped looking the same.
So one paragraph added at the top marks the whole page?
It does, and that is the most important limit of this tool. Adding text pushes everything below it down, and from there the lines no longer line up with the other version. The words are the same, the position is not. A pixel comparison has no way to tell those two cases apart.
Do both files need the same number of pages?
No. Pages in common are compared, and pages that exist in only one of the documents are identified by number, in the summary and in the final file. Nothing breaks because of it.
What if the pages have different sizes?
Both pages are reduced to a common scale before any comparison, each keeping its own proportions. Two exports of the same document at different resolutions come out as identical, which is what makes sense. Genuinely different sheet formats (A4 against Letter) show up as a difference, because the content sits on a different part of the sheet.
The tool marks the whole page and I only changed one word.
Almost certainly the change shifted the rest of the text. A longer word makes the line reflow, a new sentence pushes the paragraphs down, and from the point of the change onwards nothing lines up again. The comparison is still correct: that content did move. What it cannot do is tell you the wording is the same.
I changed the document and the tool says everything is identical.
Some changes do not move a single pixel: metadata, the author, hidden layers, an annotation that is not drawn, or a font swapped for one that draws the same. To see what the file holds inside, use PDF properties.
Areas are marked where I did not touch anything.
Lower the sensitivity. On high sensitivity, tiny drawing differences (edge smoothing between two exports) are enough to light a block up. Normal sensitivity ignores them.
I only see the first pages on screen.
The preview stops at the first twenty pages, because each one costs two renders and the wait would stop looking like an application at work. The file you download carries the whole document, up to the tool page limit.
The file has too many pages and the tool refuses before even trying.
Documents with a very large number of pages hit a safety limit before spending too much memory. The message states the limit; split the file first.
Questions about comparing two PDFs.
Do I need an account to compare PDFs?
Yes. The account (magic link, no password) is needed for the subscription. This tool is part of the Premium subscription, EUR 1.99 a month, which removes the limits on every tool and adds OCR. Sign PDF opens on the free plan, with one signature a day.
What do I get at the end?
A PDF with one sheet per compared page, both versions side by side and the differences painted over both, plus a summary of how many pages differ.
Why are the differences marked on both sides?
So you do not have to hunt for the matching spot in the other version by eye, which is exactly the work this tool exists to save.
Are my files kept on your servers?
No. Since nothing is sent, nothing is kept outside your browser.
Need to know
what changed in this version?
Open the tool and try it. Nothing to install, nothing sent anywhere.
Open Compare PDF