How to Compare Two PDF Files for Differences

Add both files to PDF Compare. The order matters: put the older or baseline version first and the newer version second, because the report describes the changes that lead from the first document to the second.

Run the comparison and download the report. It arrives as a separate PDF, with added lines marked in green with a plus sign and removed lines in red with a minus sign. If the two documents contain the same text, the report says so explicitly.

The report works through the documents page by page, and each heading states how many differences that page contains. When a page has a very large number of changes, the first two hundred lines are listed and the remainder is summarised as a count, which usually signals that the page was rewritten and is quicker to read in the source document.

Lines are shortened to stay readable, so use the report alongside the original files for anything that depends on context. Changing a single word in a clause produces both a removed and an added line, and reading the pair together makes the actual edit obvious.

The comparison matches page 1 against page 1, page 2 against page 2 and so on. If a single page was inserted, everything after it shifts, and the report will show those pages as completely rewritten even when only the position changed.

Check the page counts first when this happens. If they differ, use Page Extract to pull the equivalent sections out of both files and compare those parts instead. The same technique is useful for reviewing one chapter of a very long document.

The comparison is text based. Changes in font, size, colour, table borders, images, signature blocks and page layout do not appear in the report. To review a visual change, open both documents side by side on screen.

Scanned files without a text layer contain nothing to compare, so run PDF OCR on them first. To compare a Word document with a PDF, convert the Word file with the Office to PDF tool and compare the two PDFs.