Compare Two PDF Files
Compare two PDF files word by word, side by side, free.
Compare two PDF files: two versions of the same document. The writing on each page is read and lined up, and you see which words were added and which were taken out, side by side.
- Free, no sign-up
- Files never leave your device
- Up to 100 MB per file
The older file
Drop PDF files here
or
Up to 100 MB per file. Your files stay on your device.
The newer file
Drop PDF files here
or
Up to 100 MB per file. Your files stay on your device.
Both files stay on your device. Nothing is uploaded.
What next
- Found changes nobody mentioned? Ask about them before you sign or approve the new version.
- To point the differences out to someone else, highlight them in the new file with Annotate PDF.
Step-by-step guide: How to Compare PDF Versions of a Contract or CV
How to compare two PDFs
- 1
Choose the older file on the left and the newer one on the right.
- 2
Press “Compare them”.
- 3
Read the changed pages. Green is new, red with a line through it is gone.
- 4
Save the differences as a text file if you need to pass them on.
How the tool reads the two files and lines them up
The writing on each page of both files is read in your browser, with the same engine as our Copy text from PDF tool, so Arabic comes out joined and in reading order with numbers and English words in their places. Then page 1 is set against page 1, page 2 against page 2, and each page is split into words at the spaces.
To find the differences we use Myers’ method, the one behind git diff: it looks for the smallest number of additions and removals that turns the old page into the new one. That is why changing “thirty days” to “fourteen days” shows as one word swapped, not as everything after it. A word stuck to a punctuation mark counts as a different word, so adding a full stop shows as a small change. When two pages have almost nothing in common, more than 1,500 changes, the old and new text are shown as two whole blocks.
The two files are shown side by side, each in its own reading direction, with green for what was added and red with a line through it for what was taken out. “Only changed pages” hides the rest, and “Save the differences” writes a plain text list of every change, page by page. Nothing is written into either file.
Example: two drafts of hall hire terms
For this example we made two versions of the hire terms for a made-up community hall, two pages each. In the newer one the deposit went up from £50 to £75, and a new rule about cleaning the kitchen was added on page 2; everything else is the same.
Choose the older version on the left and the newer one on the right and press “Compare them”. The line at the top says how many pages changed and how many words were added and taken out; “£50” appears crossed out in red and “£75” in green in its place in the sentence, and the whole new rule shows in green.
This is what you want before signing a revised agreement: not reading the whole document again, only the words that changed. If both versions are scans, there is no text in them to compare, and the tool says so rather than showing an empty result.
When you would use it
Checking what a supplier changed in the second draft of a contract.
Finding the difference between two versions of a report that nobody kept track of.
Confirming that a corrected assignment really contains the corrections.
Seeing whether a file someone resent differs from the one you already approved.
What to expect
It compares words, not appearance. Moved images, changed colours and layout differences are not reported.
Scanned pages hold no text to read, so they come up empty — which includes most documents photographed with a phone.
Pages are matched in order, so a page added near the beginning makes everything after it read as changed.
The result is for reading on screen. Neither file is altered, and nothing is written back into them.
Frequently asked questions
Is this really free?
Yes, you can compare PDF documents here with no sign-up, no daily limit, and nothing to install.
Are my files uploaded?
No. Both files are read inside your browser, on your device, and neither is sent to us or anyone else. That matters more here than usual: comparing versions of a contract or a report means having two sensitive files open at once.
How do I compare two PDF files?
Choose the older version on the left and the newer one on the right, then press “Compare them”. The pages are shown side by side, with new words in green and removed words in red with a line through them. It is a quick way to check two versions for differences before you sign a revised contract or send back an edited report.
How are the pages lined up?
In order: page 1 against page 1, page 2 against page 2, and so on. If one file has more pages, the extra ones are shown on their own. This is what two drafts of the same document normally need; a page added in the middle will make everything after it look changed.
How does it find differences between two PDFs?
It looks for the smallest set of additions and removals that turns one page into the other, which is the same approach programmers’ tools use. That is why swapping one word shows as one word changed, rather than everything from there on.
Does it compare pictures or layout?
No, only the writing. Two pages with the same words in a different font or a different place count as the same. A picture that changed is not noticed at all.
Does it work with Arabic?
Yes. The writing is compared word by word whichever language it is in, and each side is shown in the direction it reads.
It says neither file has any writing. Why?
They are almost certainly scans: pictures of pages with no text inside them. There is nothing to compare until the text has been recognised, which this tool does not do.
Can I keep the result?
Yes. “Save the differences” gives you a plain text file listing every change, page by page, which you can attach to an email or keep with the two versions.
A page was added at the start of the new version and now everything looks changed. What can I do?
Pages are matched in order, so one extra page shifts everything after it. Take that page out of a temporary copy with Delete pages, compare again, and only the real changes are left.
Why can’t I open my password-protected PDF?
Protected files are encrypted, so the writing inside can’t be read. Remove the password first, then try again.