How to Compare Two Versions of a Contract or PDF and Spot Every Change

Words or lines?

The tool offers two granularities.

Words marks each changed word. Use it for contracts, policies and any document where most text stays the same and small edits matter. You'll see "within 30 days" turn into "within 60 days" with only the number highlighted.

Lines marks whole lines or paragraphs that differ. Use it when a document has been heavily rewritten or restructured. Word mode on a heavily edited document produces a dense patchwork of red and green that's hard to read; line mode gives a clearer overview of which passages changed.

A good approach: start with lines for an overview of where changes cluster, then switch to words to read each changed section closely.

Step by step

1. Open Compare PDF.
2. Drop the original (your last version) into the left box.
3. Drop the changed version (theirs) into the right box.
4. Choose Words for contracts.
5. Click Compare.
6. Read the counters: "+48 added, −31 removed" tells you at a glance how much moved.
7. Scroll through the highlighted text. For each change, note the section and decide whether you accept it.

Narrowing the comparison

For long documents where only some sections matter, extract the relevant pages from both versions first with Extract PDF Pages. Comparing pages 10 to 15 of each gives a shorter, focused result. Be careful to extract the matching pages: if the new version added a page, the page numbers may have shifted.

Reading the results

What's highlighted

• Green: text in the new version that wasn't in the old one.
• Red with strikethrough: text in the old version that's gone from the new one.
• Plain: text that's identical.

A replaced word shows as a red old word followed by a green new one: reasonable best.

What isn't highlighted

The comparison covers text only. It doesn't detect:

• changes to images, logos, signatures or stamps
• formatting changes: bold, font, colour, spacing
• layout changes: a paragraph moved to the next page, different margins
• changes inside scanned pages (they contain images, not text)

If the document's meaning depends on something visual, such as a chart, a map or a signature block, check those pages by eye.

Traps and false alarms

Hyphenation and line breaks

If one version was exported from a different program or with different margins, words may break across lines differently. The tool rejoins hyphenated words, but a few may remain as false differences. A red "agree-" next to a green "agreement" is a line-break artefact, not a change.

Ligatures and special characters

Some fonts combine letters like "fi" and "fl" into a single character. Curly and straight quotes, different dash types and non-breaking spaces can also differ between exports. These may show up as tiny changes that don't affect meaning.

Headers, footers and page numbers

If page numbers or running headers changed position, they may appear as changes scattered through the text. Mentally filter them, or crop them away with Crop PDF on both versions before comparing.

Scanned documents

If either version is a scan, there's no text to compare and everything shows as added or removed. Ask for a digital copy, or run OCR on the scan first, accepting that OCR errors will appear as differences.

Moved text

When a clause is moved, a text comparison shows it as removed in one place and added in another. Watch for blocks of red and green with the same wording: that's a move. Then check whether the move changes the meaning, for example by placing a clause under a different heading.

A review routine for negotiations

Comparison tools are most valuable in contract negotiations, where drafts go back and forth several times. A routine keeps you in control.

1. Keep a clean version history

Save every version you send and receive, named with the date and the sender: 2026-10-03-Supply-Agreement-OURS.pdf, 2026-10-07-Supply-Agreement-THEIRS.pdf. Never overwrite.

2. Always compare against what you sent

Compare their draft with the version you last sent, not with the original or with an earlier draft. That isolates exactly what they changed this round.

3. Don't rely on their markup alone

Many people send a "redline" showing their changes with Word's track changes. Track changes are helpful but not reliable: changes can be made with tracking off, or accepted before sending. Run your own comparison on the clean versions every time.

4. List every change

Make a simple table: section, old text, new text, your position (accept, reject, discuss). It becomes the agenda for the next call and a record of what was agreed.

5. Compare the final against the agreed text

Before signing, compare the signature version against the last version you agreed. This catches last-minute changes, intentional or not, slipped into the "final".

6. Compare what comes back signed

When the countersigned document returns, compare it with the version you signed. It should be identical apart from signatures.

Beyond contracts

The same technique works for:

• Policy updates: see what changed in a new privacy policy or employee handbook.
• Terms of service: compare a service's new terms with the old ones.
• Academic work: check what an editor changed in your manuscript.
• Reports: find what changed between a draft and the published version.
• Regulations and standards: compare a new edition with the previous one.
• Your own drafts: see what you changed since you last sent a document for review.

When you need more

Browser comparison covers text, which is what matters in most documents. For some jobs, other tools fit better:

• Word's Compare feature (Review, Compare) compares two .docx files and produces a tracked-changes document. If you have the Word sources, use it; it also shows formatting changes.
• Professional comparison software used by law firms compares PDFs including formatting and produces formal redline reports.
• Visual comparison tools overlay two PDF pages to show pixel differences, useful for drawings and designed layouts.

If you only have PDFs and need an editable document of the new version, convert it with PDF to Word and use Word's comparison against your own Word version. To quickly grab the text of a changed section for an email, use PDF to Text.

Building the change list

The change list from step 4 of the routine is worth getting right, because it turns a comparison into a negotiating tool. A simple format that works:

Clause	Their change	Effect	Our position
4.2 Payment	30 → 45 days	Cash flow delayed 15 days	Reject; offer 35
9.1 Efforts	added "commercially"	Weaker obligation	Discuss
12.3 Liability cap	12 → 3 months of fees	Recovery cut by 75%	Reject
Sched. B	carrier delays excluded	Penalties avoidable	Accept if capped

Write the "effect" column in plain language. It forces you to understand each change rather than just noting it, and it helps colleagues who weren't part of the negotiation. Keep the table with the version files so the history is clear later.

A worked example

A supplier returns a 24-page supply agreement with an email saying "minor clarifications only".

The comparison shows +62 words added and −40 removed. Line mode shows changes clustered in four places. Word mode reveals:

1. Clause 4.2: payment terms changed from "30 days" to "45 days". Not minor.
2. Clause 9.1: "reasonable efforts" became "commercially reasonable efforts". A softer obligation for the supplier.
3. Clause 12.3: the liability cap changed from "the fees paid in the preceding 12 months" to "the fees paid in the preceding 3 months". A large reduction in what you could recover.
4. Schedule B: a new line excluding "delays caused by third-party carriers" from service level penalties.
5. Several hyphenation differences on pages 7 and 18, which are false alarms.

Four substantive changes, none mentioned in the email. The review takes ten minutes, and you go into the next call with a precise list.

Keeping comparisons confidential

Contracts under negotiation are among the most sensitive documents a business handles: prices, liability positions, internal deadlines. Many online "compare PDF" services upload both files to their servers. That puts two versions of a confidential agreement, and the exact differences between them, on a third party's machines. The browser tool avoids that: both documents are read and compared in your tab. If your firm has an approved comparison tool, use it; otherwise prefer tools that process locally.

Common questions

Can I compare a Word document with a PDF? Export the Word file to PDF first, then compare the two PDFs.

Does it compare tables? It compares the text inside tables. Changed numbers show up; changes to the table's layout don't.

How long can the documents be? There's no fixed limit. Very long documents take longer and the results get long; extract the relevant sections for faster reviews.

Are my contracts uploaded? No. Both files are processed in your browser.

Why are there differences in text that looks the same? Usually hyphenation, special characters or spacing. Read the highlighted words in context.

How long does a comparison take?

For a typical 20 to 40 page contract, extraction and comparison take a few seconds in a modern browser. Reading the highlighted result takes five to fifteen minutes, depending on how many changes there are. That's a fraction of the hour or more a careful side-by-side reading needs, and far more reliable.

Summary

Never trust "minor changes" without checking. Keep every version with clear names, compare each incoming draft against the version you last sent, use word mode for contracts and line mode for rewrites, and list every substantive change before you respond. Watch for false alarms from hyphenation and headers, and check visual elements by eye. Comparing the final and the countersigned versions before and after signing closes the loop. A few minutes with a comparison tool is cheap insurance against the clause you would otherwise have missed.