PDF Redline Comparator

DrawDiff

See exactly what changed. Pixel by pixel.

Pixel-accurate overlay comparison for engineering drawings, technical documents, and contracts. Color-coded redlines show every addition, deletion, and unchanged element at a glance.

▶ Launch DrawDiff How it works ↓
DRAWDIFF — REDLINE OVERLAY PREVIEW
Original
Revised
Overlay
Original only (removed)
Revised only (added)
Unchanged (both)
🔒
100% Local Processing
Your files never leave your device
🚫
No Uploads
No server receives your documents
🔑
No Account Required
Open and use — nothing to sign up for
🛡️
CUI / Proprietary Safe
Safe for sensitive and controlled documents
How It Works

Three steps to a redline.

No installation. No account. Open DrawDiff in any modern browser and you're ready.

01
📄
Load Your PDFs
Drag and drop your original and revised PDFs into the tool. Multi-page documents are fully supported — all pages compared in order.
02
⚙️
Run Compare
Hit Run Compare. DrawDiff renders each page at high resolution and performs a pixel-by-pixel comparison. Progress updates in real time.
03
🔍
Review & Export
Pan and zoom the color-coded overlay. Inspect specific regions, export individual pages as JPGs, or package everything into a single PDF redline.
Color Code

Read a redline in seconds.

Green — Original Only
Content present in the original PDF that has been removed or moved in the revision.
Red — Revised Only
New content added in the revised PDF that wasn't in the original.
Cyan — Unchanged
Content present in both PDFs within the diff threshold — nothing changed here.
Dark — Background
Empty space. Background color is adjustable — dark, white, or original document background.
Features

Built for real drawing review.

Every feature exists because engineering drawing comparison has specific problems that generic tools don't solve.

🎯
Pixel-Accurate Overlay
Every pixel compared at configurable render scale. Catch even the smallest line weight change or dimension edit.
📑
Multi-Page Support
Compare entire drawing sets. All pages processed in one run — page 1 vs 1, page 2 vs 2, across hundreds of sheets.
⊕
Alignment Tool
When a view shifts between revisions, the standard compare becomes noise. Crop a region, pick a reference point on each, and compare aligned.
🔎
Region Inspector
Ctrl+drag any area to pop up a three-panel view — overlay, original, and revised side by side. Copy to clipboard or save as JPG.
🎨
Custom Colors
Change the diff overlay colors to suit your workflow. Presets for neon, print, and colorblind-safe palettes built in.
⬇
Flexible Export
Export all pages as individual JPGs with a custom filename prefix, or package the entire comparison into a single PDF document.
Use Cases

Who uses DrawDiff.

Anyone who needs to understand exactly what changed between two versions of a document.

🏗️
Engineering Drawing Review
Compare MIL-spec drawings, CAD exports, and technical revisions. Catch dimension changes, added notes, and modified tolerances.
🏛️
Architecture & Construction
Review plan revisions and change orders. Identify what moved, what was added, and what was removed between drawing sets.
⚖️
Legal & Contracts
Redline contract amendments and regulatory filings. See every word-level change without manually reading every page.
🛡️
Defense & Government
Safe for proprietary and CUI documents. Nothing leaves your machine — no upload risk, no firewall concern for local use.
Get Started

Ready to see
what changed?

Free to use. No signup. Works in any modern browser. Your documents stay on your machine.

▶ Launch DrawDiff Free