Compare two PDF files and see the differences
Compare two PDFs and find what changed between them. Upload both versions and see the textual differences instead of reading two documents side by side hoping to spot an altered clause. Free, immediate, and nothing to install.
Reading two versions of a long document to find what changed is a task humans are genuinely bad at. Attention drifts after the first few pages, and the differences that matter most are precisely the ones designed not to stand out — a "shall" changed to "may", a figure adjusted by one digit, a negation quietly inserted or removed.
Word's track changes solves this within Word, but PDFs arrive without any change history. The recipient of a returned contract has the sent version and the returned version and no indication of what happened in between beyond whatever the other party chose to mention.
Automated comparison finds every textual difference regardless of how small or how deliberately unobtrusive.
This is where the tool matters most. You send a contract, the other side returns it saying they made "a couple of minor amendments", and the honest answer is that you cannot easily verify that claim. Reading forty pages of legal text closely enough to catch a single altered word is slow, and the consequences of missing one can be significant.
Comparing the sent version against the returned one surfaces every change, including any that were not mentioned. Most of the time the changes are exactly what was described. Occasionally they are not, and finding out before signing rather than afterwards is the entire value of the exercise.
Anyone reviewing a returned contract — the single most common and most valuable use. Compliance teams checking what changed between policy revisions. Editors and publishers verifying that a corrected proof contains the corrections and nothing else. Procurement teams comparing supplier quotations across revisions. Anyone with two files named final and final_v2 who needs to know what actually distinguishes them.
Upload both documents — typically the original or sent version and the revised or returned version. The comparison runs and the textual differences are reported. Work through them and evaluate each one, since the tool tells you what changed but only you can judge whether a given change is acceptable.
Not every reported difference is a meaningful edit, and knowing why helps you read the output efficiently.
Reformatting produces false positives. Changing a font, adjusting margins, or altering line spacing shifts where words break across lines, which can register as differences even when the wording is byte-for-byte identical.
Conversion artefacts appear. If one version passed through a different tool on its way to PDF, small variations in character encoding and spacing can show up.
Scanned pages are unreliable. Two scans of the same page are never pixel-identical, and OCR of each produces slightly different text.
The practical approach is to scan the reported differences quickly, dismiss the ones that are obviously formatting noise, and examine closely the ones that change meaning.
A scanned PDF has no text to compare. Run both files through Extract Text (OCR) first to obtain text layers. Be aware that OCR is not perfect and its errors will appear as differences, so results from scanned sources need more careful interpretation than comparisons between digital documents.
Both documents are processed in memory and discarded once the comparison completes. Nothing is written to disk, nothing is logged, and no copy of either file is retained — which matters given that contracts and confidential agreements are exactly what people bring here.
Extract Text (OCR) prepares scanned documents for comparison. PDF Metadata shows creation and modification dates, which sometimes clarifies which version came first. Extract Pages lets you compare just one section of two long documents.