The other side sent the contract back "with the agreed changes". It's 80 pages long. You know the price-adjustment clause changed — but what else did? Rereading everything side by side takes a whole afternoon, and fatigue makes your eyes skip exactly the line that matters.
Long documents are where automatic comparison makes the biggest difference. This guide shows how to do it in practice and what to expect from the free and Pro plans.
Why long documents are the worst case for manual review
The bigger the PDF, the more human error weighs in:
- Attention drops over time — page 60 gets far less care than page 3;
- Reformatted paragraphs move to another page and throw side-by-side reading out of sync;
- Small changes — a number, a comma, a "not" — vanish inside long blocks of text;
- Whole inserted passages push everything else forward, and parallel reading loses its rhythm.
Automatic comparison solves this by reading the text of both files and marking exactly what was removed and what was added — no matter which page it ended up on.
How to compare two long PDFs in RoseLab
- Open the PDF comparison tool;
- Drag the old version onto the left panel and the new one onto the right (or use the open buttons);
- Turn on Highlight differences: removed passages appear in red on the left and added ones in green on the right;
- Use the arrows to jump from one difference to the next — both sides move to the right spot;
- To read calmly, turn on synchronized scrolling so both documents move together.
Your files are processed in your browser — nothing is sent to servers. And if a PDF arrives password-protected, the tool asks for the password and opens it right there (see how it works).
What you can do on the free plan
You can use the comparison tool without subscribing. With large PDFs, the free plan works as a preview:
- It shows and compares the first 20 pages of each document;
- It highlights the first differences found in that section;
- A bar at the top tells you how many pages the document has in total.
That already covers many cases: when the change is near the beginning (parties, subject, price), when you want to check the tool works well with your files, or when the document has up to 20 pages — then it opens in full.
When it's worth comparing the whole document
On the paid plans, the tool opens every page, highlights every difference and generates a PDF comparison report, with the list of changes and the fingerprint (hash) of each file — useful to attach to an opinion or to show a client exactly what changed.
For anyone who reviews contracts, tenders or reports every week, it's what saves the afternoon of rereading. Prices are on the plans page.
Tips for a more reliable comparison
- Compare the right versions. It sounds obvious, but comparing "final version" with "final version 2" happens a lot. Check dates and names first.
- Scanned PDFs have no text. If the document is a scan (just images), there's no text to compare automatically — both sides still open side by side for reading, but without highlights. Ask for the original PDF whenever you can.
- Signed version = approved version? After reviewing, confirm that the file that came back signed is exactly the one you approved. We explain how in how to check if two files are identical.
- Separate attachments. If the contract came with appendices in the same PDF and you only need to check the main body, use Remove pages or Split PDF to separate the parts first.
For a step-by-step focused on short and medium contracts, see also how to compare two versions of a contract PDF.
Ready to put it into practice?
Free, no sign-up — and your files never leave your computer.
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