Side-by-side or overlay PDF diff driven by one engine that reads each file into a structured model — text, vector geometry, images, form fields, annotations — and compares the models. Moves show as moves, edits show only where they happened, and any PDF type works without picking a mode.
Open a STEP / STP part and it measures itself — volume, thinnest wall, draft and undercut checks on load, plus hole detection with a BOM. Measure, section, export STL. Rust + WASM B-rep kernel, runs in your browser.