CRYPT-hack/CAD-pdf-comparison ? reverse-engineered prompt

Build me a local PDF drawing comparison tool for redline review that runs in the browser and never uploads files anywhere.

I want to load a previous version and a revised version, pick which pages to compare, and then see the differences clearly in a side by side review and an overlay. It should support simple page alignment, automatic alignment when the sheet shifts a little, and a manual mode where I can pick the same three points on both drawings if the automatic match is off. I also need a way to crop the compare area so title blocks and notes do not create noise.

Please include change navigation, a list of detected changes I can export to CSV, and a way to generate a marked up PDF with cloud style callouts. Keep the interface clean and practical for drawing review, with sensible defaults that work well for engineering sheets. If you need current browser or PDF library docs, look them up online.