How to compare PDFs in Adobe Acrobat — and without Acrobat Pro
To compare PDFs in Adobe Acrobat, open All tools, choose Compare files, pick the old version on the left and the new one on the right, and click Compare. Adobe lists it as an Acrobat Pro feature. Without Pro, Compare PDF diffs the text of both files free in your browser.
Acrobat has a built-in comparison tool, but it lives in the paid tier, which is why "I do not have the compare tool" is one of the most common Acrobat questions. This covers the Acrobat route as Adobe documents it, the free route when you only have Reader, and what a line-by-line text comparison will and will not flag.
How do you compare PDFs in Adobe Acrobat?
Open Acrobat, go to All tools and choose Compare files. Select the old version on the left and the new version on the right, then click Compare. Adobe's help page says Acrobat opens a results document with a summary of the changes, and that a Compare text only option skips images and formatting.
Does Adobe have a PDF comparison tool?
Yes. Adobe calls it Compare files, and its own help page titles the feature as Acrobat Pro. The free Acrobat Reader does not include it, so if All tools has no Compare files entry, that is usually why. The Acrobat Pro trial is the official way to try it.
How do I compare two PDFs without Acrobat Pro?
Open Compare PDF in any browser, drop the original on the left and the changed file on the right, and click Compare PDFs. It reads the text of both with pdf.js and diffs them line by line, free, with no account, and neither file is uploaded.
Open Compare PDF
Go to Compare PDF. It runs in the browser tab, with nothing to install.
Add both versions
Drop the original PDF in the Original box and the newer one in the Changed box. A scan needs OCR PDF first, and a password-protected file needs Unlock PDF first.
Compare and read the diff
Click Compare PDFs. Added lines are highlighted in lime with a plus sign, removed lines are struck through on a red tint, and a line above the diff counts how many lines were added and removed.
Can I compare two PDF documents for differences in the wording?
Yes, and the unit is the line, not the word. We ran a four-line lease clause through the real comparison code with one word changed, fifty to sixty. The diff marked that whole line as removed and the new line as added. Reading the two lines against each other shows which word moved.
Two more results from the same test are worth knowing. A capital letter added to one word was flagged. An extra space typed between two words was not, so do not count on spacing-only edits showing up.
Why does one small edit flag several lines?
Because the text reflowed. In our test, inserting the single word "promptly" into the first line pushed a word onto every following line, and the diff reported three lines removed and three added. The same thing happens at a page break: a line that moved to the next page showed as a removal and an addition, with no wording changed at all.
How can I compare two PDF files side by side?
Acrobat Pro shows the two files side by side with the changes linked, according to Adobe. Compare PDF does not lay the pages out; it merges both versions into one marked-up column. It also does not say which page a change is on, so search the changed PDF for the flagged line to find it.
A text diff is blind to appearance. In our test, the same clause set in a different font and coloured red came back as "No text differences found". If a designer changed the layout, the images or the colours, Acrobat Pro's full comparison is the one that will see it. If what matters is the wording of a contract or a spec, a text diff answers the question directly. For the general walkthrough, see how to compare two PDFs.
