Might be better to provide a downloadable executable instead of asking the user to trust that the browser isn't doing what the browser was designed to do.
There are already free PDF editors that can be downloaded and installed once forever. What I used most is Libreoffice Draw: it imports a PDF, edit it as if it were a file in its own format, export as PDF again. It's not the only choice. Firefox has had a vanilla PDF editor since last year: download a PDF or drag one inside the browser window, edit it, save it. It's enough to add a PNG of my signature and fill out forms.
Local-only web apps are great one-off projects, but extensions and native apps require much more maintenance.
In addition to the web site, the Electron app and the Chrome extension, you may want to distribute a command-line version of your tools as WASI-style .wasm program files. If you do so, I would exclusively use the them this way, from the command line.
Running an executable is a risk by default and the way it interacts with my network is way less transparent. I honestly prefer this in the browser.