No connection? The tools still work.
Your PDFs never travel to a server, so they never needed the network. Once you have opened a tool page while online, this browser keeps a copy of it and of the engine, and you can compress, merge, sign or redact with Wi-Fi off.
Try it. Open the compressor, switch on airplane mode, then drop a PDF. It runs exactly as before: this is the simplest proof that nothing is uploaded.
What is saved. The tool pages and the engine files (pdf-lib, pdf.js, qpdf). OCR language data (8–10 MB per language) is saved the first time you run OCR. Your files are never saved by the offline copy; recent jobs you download are kept only in this browser’s own storage, and you can clear them from your desk.
What needs the network. Official form pages (they fetch the agency’s current edition), upload-limit records, sign-in, alerts and presets. Those load when you’re back online.
Checking this browser’s offline copy…