Use the free PDF Text Comparer below: your PDF never leaves your browser — all work happens on your device, and nothing is uploaded to any server.
Why compare two PDFs?
Documents change, and the changes are not always obvious. A contract comes back with a clause reworded. A report is revised and a paragraph quietly disappears. Two versions of a manual look identical until you find the one safety note that moved. Reading both side by side and spotting every difference by eye is slow and unreliable. A comparer does the dull, exact work for you: it extracts both texts and shows what is only in one version.
Lawyers check redlines. Editors check revisions. Teachers check whether a resubmitted essay actually changed. Students compare their draft with a final version. In every case, the question is the same: what changed, exactly?
How this tool compares
Upload both PDFs. The tool extracts the text of each with pdf.js, splits it into sentences, and compares the two sentence sets. Sentences that appear only in the first PDF are shown as removed. Sentences only in the second are shown as added. It also counts sentences in each document, so you can see at a glance whether the new version grew, shrank, or just shuffled.
All of this happens in your browser. Neither PDF is uploaded, which matters a lot when the documents are contracts, drafts, or anything confidential. The comparison is private by design.
Reading the result well
Start with the added sentences. Additions are usually the point of a revision: new terms, new findings, new instructions. Then read the removed sentences. Removals are where risk hides, because something you relied on may have vanished without a note. If a sentence was only reworded, it will show up as one removal and one addition that say nearly the same thing. That is normal, and it tells you exactly where to look in the original documents.
Do not treat the comparer as a legal opinion. It finds text differences; it does not judge whether a change matters. A changed comma can matter in a contract, and a rewritten paragraph can matter not at all. Use the tool to find the differences, then use your judgment on each one.
When sentence comparison is enough, and when it is not
Sentence comparison is excellent for prose: reports, essays, policies, manuals. It is weaker for tables and numbers, where a single changed digit inside a long sentence still shows the whole sentence as changed. That is still useful — it points you at the right sentence — but you must read the numbers yourself to see what moved.
It is also weaker when the layout changed but the words did not. If a document was reformatted with identical text, the comparer will correctly report no differences, even though the pages look different. For layout questions, compare the PDFs visually instead.
A practical revision workflow
Keep both versions with clear names, such as contract-v1 and contract-v2, and never overwrite the old one. Run the comparer and save or note the added and removed sentences. Then open the new PDF and check each flagged change in context, because a sentence alone can mislead — the surrounding paragraph decides its meaning. Finally, write a one-line summary of the changes for anyone else who needs to approve the new version.
That habit turns revision from a chore into a record. Months later, when someone asks what changed in version two, you have an answer instead of a memory.
Common questions
Does it compare images or layout? No. It compares extracted text only, sentence by sentence.
What if the PDFs are scans? Scans have no text layer, so there is nothing to compare. Run OCR on both first.
Can it compare more than two PDFs? Not in one run. Compare them in pairs, newest against previous, and chain the results.
Are my documents private? Yes. Everything runs locally in your browser and nothing is uploaded.