PDF Comparison for Engineering Drawings

When Revision B arrives, you need to know exactly what changed from Revision A — every moved dimension, every added weld symbol, every deleted note. DrawDiff gives you a pixel-accurate overlay in seconds, with no file upload required.

    🔒 Your drawings never leave your device. All comparison runs in your browser. No server, no upload, no account — critical for controlled and sensitive documents.
  

The Problem with Manual Drawing Review

Comparing two revisions of a technical drawing by eye is slow, error-prone, and expensive. Printed side-by-side review misses subtle changes. Trying to overlay PDFs in Acrobat gives you text-diff results that don't work for graphical content. And cloud-based tools require uploading proprietary designs to a server you don't control.

Engineering teams need something faster, more accurate, and privacy-safe.

How DrawDiff Works for Engineering Drawings

DrawDiff renders both PDFs at high resolution (up to 8× scale, 576 DPI) and performs a pixel-by-pixel comparison. The result is a colour-coded overlay that shows exactly where the drawings differ:

Green — in original only (deleted in revision)

Red — in revision only (added or changed)

Cyan — unchanged between revisions

Every line, symbol, dimension, and annotation is compared at the pixel level — nothing is missed.

Features Built for Technical Drawings

⊕

Alignment Tool

When views shift between revisions, pick matching reference points on each drawing and DrawDiff aligns them before comparing. Supports scale compensation for views drawn at different scales.

◎

Find Differences

Automatically clusters changed pixels into numbered regions. Jump to any difference, export a JPG with numbered boxes — ready for a change log or review markup.

Ⓣ

Text Compare

Select a region and extract text from both PDFs. Get a word-level diff of annotation changes, tolerance callouts, or title block revisions.

🔍

Region Inspector

Ctrl+drag any area to open a three-panel popup showing the overlay, original, and revised side by side at full resolution. Save as JPG or copy to clipboard.

Typical Engineering Use Cases

IFC / Issued For Construction drawings — confirm what changed between issued revisions before forwarding to site
Supplier drawing approval — compare vendor drawing against your spec or previous submittal
Design review — catch unintended changes introduced during drafting
As-built verification — compare as-built drawings against design drawings
Multi-discipline coordination — overlay structural and MEP drawings to spot conflicts

Works With Any Engineering PDF

DrawDiff works with any PDF — CAD exports (AutoCAD, SolidWorks, Revit, MicroStation), scanned drawings, and PDFs from any source. For scanned drawings, the pixel comparison catches everything even when the PDF contains no extractable text.

Multi-page support handles complete drawing packages — compare every sheet in one run, navigate page by page, and export individual sheets or a full PDF of the redlined set.

Free to use. No account. No upload. Works in any modern browser.

▶ Compare Drawings Now