WrenPDF

Compare PDF

Compare two PDFs at text level and see which lines were added or removed. Ideal for contract revisions and version checks.

What it does

Reading two versions of a contract line by line to spot what changed is tiring and easy to get wrong. This tool extracts the text of both PDFs, lines them up and highlights additions in green and deletions in red, with an overall similarity score.

The comparison is text-based: font, colour and image changes are not reported. Options to ignore case and whitespace keep the focus on changes that matter.

How to use it

  1. Drop the two PDFs you want to compare.
  2. Differences are computed automatically and the changed regions are listed.
  3. Optionally download the report as a text file.

When is it useful?

  • Seeing what the other side changed in a contract revision
  • Comparing a new version of a specification or policy with the old one
  • Checking different drafts of an essay or report
  • Catching price and clause changes between quotes

Tips

  • Turn on "ignore whitespace" first; it removes noise from reflowed lines.
  • Download the report as a text file to keep a record of the differences.
  • Scanned documents have no text, so they cannot be compared until you run OCR PDF.

Frequently asked questions

How does the comparison work?
The text of both PDFs is extracted page by page and the lines are aligned. Added lines appear in green, removed lines in red. Scanned documents with no text layer have nothing comparable to extract.
Do formatting differences show up?
No. The comparison is text-level: font, colour, size and image changes are not shown. The goal is to catch textual changes across contract and report revisions.
How many pages can it handle?
There is no fixed limit, but very large documents (thousands of lines) slow the comparison down. The algorithm automatically switches to a faster method and warns you.
What about case and whitespace differences?
You can turn on "ignore letter case" and "ignore whitespace". While they are off, every character difference is reported.
Are my files uploaded?
No. Both text extraction and comparison happen in your browser, inside a separate Web Worker.
What if pages were reordered?
The comparison follows the flow of text. A section that moved shows as deleted in its old place and added in its new place.

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