# What is document comparison?

> Document comparison lines up two versions of a file and marks every change. How to run a PDF compare, read the result and catch quiet contract edits.

Source: https://learn.ynteractive.com/content/glossary/document-comparison · Updated 2026-10-19 · Free from Stepthrough (https://learn.ynteractive.com)

[Business](https://learn.ynteractive.com/content/glossary#topic-business) · [AI glossary](https://learn.ynteractive.com/content/glossary)

Quick answer

Document comparison is a tool that lines up two versions of the same file, such as the contract you agreed to and the one you were sent back, and marks every word that was replaced, inserted or deleted. You read only what changed instead of rereading the whole thing.

Last updated October 19, 2026

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Updated October 19, 2026 · By [Robert Breen](https://learn.ynteractive.com/content/about)

## Why it matters for a small business

Revised contracts arrive with friendly notes: just a few cleanups, please sign by Friday. People reread them looking for the change they expect, and their eye slides past a number in the payment clause. That one missed number can cost more than the whole review would have, every year the contract runs.

A compare does not expect anything, so it reports the edits nobody mentioned. The skill is reading the result: start with the summary count, step through each change in order, read the new side for what it says now and the old side for what it used to say. It only works if you kept the version you actually agreed to.

## What a "small cleanups" revision changed

| Section | Version 1 | Version 2 |
| --- | --- | --- |
| 1. Users | 25 named users | 20 named users |
| 2. Fee | $1,200.00 a month | $1,350.00 a month |
| 2. Payment | Due in 30 days | Due in 15 days |
| 3. Notice to cancel | 30 days | 90 days |
| 3. Renewal increase | Up to 5% | Up to 9% |
| 6. Liability cap | 12 months of fees | 3 months of fees |

From the made-up sample agreements in the Foxit compare lesson. Version 2 also inserts a new sentence in section 5.

## In a real lesson: Foxit PDF Editor: Catch Every Change in a Revised Contract

In the free [Foxit compare lesson](https://learn.ynteractive.com/content/compare-two-versions-of-a-contract-with-foxit-pdf-editor), Dana Reyes at Bright Path Marketing opens version 1 of a Summit Cloud Services agreement, goes to the View tab and clicks Compare. Version 1 is already the Old File; under New File she chooses version 2 and clicks OK.

Foxit builds a new PDF called The result of Comparison.pdf. The Summary page counts 10 changes: 9 replacements, 1 insertion and 0 deletions. Next Change steps through them with old on the left and new on the right: yellow wavy underlines for replaced text, a blue underline for inserted text, a red strike for deleted text. The Comments panel lists each one with its old and new text, ready for a reply that asks about the [liability cap](https://learn.ynteractive.com/content/glossary/limitation-of-liability-clause) and the [auto-renewal](https://learn.ynteractive.com/content/glossary/auto-renewal-clause) terms.

[Try this lesson free](https://learn.ynteractive.com/modules/foxit-compare-contract-versions) or [read the step-by-step guide](https://learn.ynteractive.com/content/compare-two-versions-of-a-contract-with-foxit-pdf-editor).

## Common confusions

### Document comparison vs a redline

A [redline](https://learn.ynteractive.com/content/glossary/redline) is a markup the author makes to show their proposed edits. A compare is something you run yourself on two finished files, so it also catches edits the other side did not mark.

### Comparison vs version history

Version history in a shared doc tracks edits made inside that one file. A compare works on any two separate files, such as PDFs sent by email.

## Tips

- Save the version you agreed to in the contract's folder the day you agree it.
- Check the content changes before formatting changes; Foxit's summary counts them separately.
- Compare text-based PDFs. A scanned version may give poor results, so ask for the original file.

## Related terms

[Redline](https://learn.ynteractive.com/content/glossary/redline) · [Auto-renewal clause](https://learn.ynteractive.com/content/glossary/auto-renewal-clause) · [Limitation of liability clause](https://learn.ynteractive.com/content/glossary/limitation-of-liability-clause) · [Payment terms](https://learn.ynteractive.com/content/glossary/payment-terms) · [Searchable PDF](https://learn.ynteractive.com/content/glossary/searchable-pdf) · [Contract key terms](https://learn.ynteractive.com/content/glossary/contract-key-terms)

## More Business terms

[Drip campaign](https://learn.ynteractive.com/content/glossary/drip-campaign) · [Dunning](https://learn.ynteractive.com/content/glossary/dunning) · [Duplicate invoice](https://learn.ynteractive.com/content/glossary/duplicate-invoice) · [E-signature](https://learn.ynteractive.com/content/glossary/e-signature)

## Where you use it: free lessons

- [Foxit PDF Editor: Catch Every Change in a Revised Contract](https://learn.ynteractive.com/content/compare-two-versions-of-a-contract-with-foxit-pdf-editor) (Foxit, 8 min)
- [AI Contract Review in 10 Minutes using Foxit AI](https://learn.ynteractive.com/content/review-a-client-contract-in-10-minutes-with-foxit-ai) (Foxit, 10 min)
- [Check a Contract for Red Flags with Claude](https://learn.ynteractive.com/content/check-a-contract-for-red-flags-with-claude) (Claude, 11 min)
- [DomoAI: Turn a Product Photo into a Short Video for Social](https://learn.ynteractive.com/content/domoai-image-to-video-product-photo-social-video) (DomoAI, 6 min)

## AI tools that use it

- [Foxit PDF Editor](https://learn.ynteractive.com/content/ai-tools/presentations-docs#tool-foxit-pdf-editor) ([free lesson](https://learn.ynteractive.com/content/review-a-client-contract-in-10-minutes-with-foxit-ai))

[More terms by tool](https://learn.ynteractive.com/content/glossary/ai-tool-terms)

## Frequently asked questions

**How do I compare two PDFs?**

In Foxit PDF Editor, open the older file, go to the View tab and click Compare, choose the newer file as the New File and click OK.

**Why does the change count look higher than the real edits?**

Some changes get two marks, for example a number written in words and in digits. In the lesson, 10 marks covered seven real changes plus the version note.

**Does a compare tell me if a change is fair?**

No. It shows what changed, not whether you should accept it. Use the list to ask the sender, and ask a lawyer about anything large.

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