i am sorry to ask, but the service looks like a cloud base solution, so if i will drop the pdf to test box, will you store it? or remove the ref?
One way to verify is to open the Network tab in DevTools and see if any requests are made when editing the PDF.
That’s exactly why I suggest installing it as a PWA and then disabling network access on the PWA. In my opinion, that’s actually the best way to use it.