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A personal workflow research project by an architectural designer

Stop hunting for what changed in your drawings.

A 100% local PDF comparison tool for architectural drawing sets. No cloud upload, no subscription, no GPU required.

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Windows 64-bit · Portable App · CPU Optimized

Split mode supports side-by-side checks, and Diff mode highlights added content in red and removed content in blue.

Workflow

Three connected steps for practical drawing review

The flow keeps review moving: import, compare, and decide - without switching between tools.

1. Load & Align (Page Review)

Drop in your Before and After PDF sets and arrange the pages to match. The built-in similarity score automatically calculates the match percentage for every pair, helping you instantly catch sheet mismatches or scale issues before the actual review even begins.

1. Load & Align (Page Review)

2. Compare & Cloud (Diff Mode)

Spot differences instantly using the Split or Diff viewing modes with fully synchronized zoom and pan. PDF Diff automatically detects changed regions and generates Cloud Marks around them (either automatically during comparison or on-demand), completely eliminating manual markup time.

2. Compare & Cloud (Diff Mode)

3. Export the Deliverable (Export)

Select the changed pages and export your results to PDF or PNG. The PDF export flattens the background drawings to protect the source files, while preserving your Cloud Marks as native, editable annotations—ready to drop directly into your team's standard Acrobat workflow.

3. Export the Deliverable (Export)
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Quick Answers

Short answers to the questions people ask first.

0 cloud uploads

Data handling

All comparison stays on the local machine.

$0 cost

Price

Free for personal and commercial use.

<7s per page

Comparison speed

Typical comparison completes in under 7 seconds per page.

Is PDF Diff by AEC DX Labs free to use?

Yes. It is free for personal and commercial use, with no licensing fee.

Does it keep drawing files offline?

Yes. Comparison runs locally on your PC, and drawing files are not uploaded to external servers.

What does it need to run?

Windows 64-bit, at least 4GB RAM, and no GPU required. Typical comparison completes in under 7 seconds per page.

Why did you build PDF Diff?

I built it after repeatedly seeing manual revision checking slow down AEC review work and introduce avoidable misses.

Maker Context

I am an architectural designer based in Tokyo. Across AEC workflows, I kept seeing teams spend too much time manually checking revised drawing sets, losing focus in the process and increasing the chance of missed changes.

I started building PDF Diff as part of my self-improvement effort. Using AI-assisted tools, I mapped the tool requirements and built a secure offline application to test whether the workflow could be simplified without changing how teams already work.

I validated the concept using sample drawing sets in a personal test environment. The tool performed as designed, completing comparisons locally in under 7 seconds per page with no external data transfer. I am publishing it as a free resource for the AEC community as part of my ongoing self-improvement research (自己研鑽).

FAQ

Trust and FAQ

Core trust signals stay visible alongside the questions people ask first.

Trust Signals

Short operational assurances for IT and security review.

Offline by default

No cloud dependency in the review path. Drawings stay on your workstation.

IT-audit aligned

No external transmission route helps teams explain data handling in security reviews.

Practical hardware fit

CPU-optimized, runs on standard workstations without additional hardware.

Common Questions

Comparison results should be verified by a qualified professional. AEC DX Labs accepts no liability for missed changes or errors in comparison output.