Earlier quoted context omitted.
> Preview.app been the best non-Adobe way to use PDF’s for decades now Where is all this stuff coming from? Why would you say Preview is the best? Foxit? Nitro? Their are endless PDF applications much more powerful and capable, some designed for professionals.
For annotating and adding a hand drawn signature to PDFs, preview really is the best: lightweight, straightforward, free, comes with the OS. I don’t know any comparable app for Linux (or windows although I rarely use it)
It’s local only (the document you load and data you fill in never leave the browser) and free
Disclosure: I’m the developer behind it