Linux

Okular works fine.

Rather than editing PDFs directly, might it be possible to use LibreOffice (LO) Writer? Write, with all the features/facilities of a document editor that will likely meet all your needs. When the document is complete, export as PDF and e-sign the PDF with LO as well..

LibreOffice is community driven and developed software project, not the product of an American company.

'Bates' numbering: LO Writer supports creating custom page numbering formats/styles.

e-sign: e-sign the PDF with LO as well, reference links below

Workflow

an example workflow might be:

• Create document templates, save read-only in network accesible location; only the template maintainer can edit/save the templates; law firm logo, letter head, watermarks, Bates numbering, etc.,
• Author copies desired template to author's system and makes the copy writable,
• Edits/saves drafts locally on author's system, or in a central, network accessible repository; backups, team access, preliminary/formal reviews, etc.
• When final version is complete, export as PDF, and of course, save it as well
• e-sign PDF using LO

References

https://knowledge.digicert.com/tutorials/sign-openoffice-libreoffice-documents https://duckduckgo.com/?q=libreoffice+pdf+esign&t=vivaldim&ia=web

The law firm that I work for is has finally decided that we should embrace Linux.

Never thought I'd read this sentence. I don't have any recommendations, just wanted to say congrats on achieving the unthinkable!

Bonus points: It's a non-American company

As an American, keep doing this. Make it fucking hurt them. A lot.

If you'd be fine with having a docker container running, have a look at Signature PDF.

I've been using it to manipulate pdfs in similar ways you described and put it on a pi in my homenetwork (autostarting docker would also work).

They have a tester here.

(Also: french open source project)

Editor, guys. They want a pdf editor.

That said, editing pdf is kinda a broken concept. Pdf is made to represent, not to edit. Better edit the source that created the pdf.
But if you have to, look for a vector editor, like Inkscape. To save again as pdf, use export.

I remember Okular having a decent set of features. It might be worth checking out. The webpage says it supports digital signing, which is a suprise to me because that's always been a hassle on linux for me. https://okular.kde.org/

I don't know every detail of your use cases, but my offline go to is xournal++ (xournalpp).

I use it for many of those actions. We moved to Germany and having a GUI pdf editor for signing, highlighting, redacting, pulling pages, etc has been invaluable.

My wife also uses it for her class lectures. She does math, so she uses a tablet to write on her slides (pdfs) live in class to talk through the material. Then, she saves the lecture PDF to give to students with the notes.

BentoPDF - bentopdf.com. It can handle anything you might need to do with a PDF. It requires docker, but thats easy enough to do on an individual machine. Your corporate setting adds some complications no doubt, and they may be looking for an actual company-backed app. I'm not very familiar with the commercial PDF editor market.

Stirling pdf

Once I needed to edit text under pdf and onlyoffice worked for me and okular can handle all of those

OnlyOffice

I personally decided for master PDF Editor and I'm pretty, happy. I do not need e-sign though but stamp-signatures.

Libreoffice suite allows you to export any document in pdf. Libreoffice Draw I use to edit pdf content. PdfArranger is a very nice tool to change the structure of a pdf (like adding a pdf file to an existing pdf, or deleting pages, you see all the pages at once on the screen and can see the content when you zoom, very intuitive). When I need to add signatures or raster pictures with transparency, I open the required page on Gimp and "File->Open as layer" the picture. Usually it works with Draw directly.

I have been working several years like this and it is pretty much a no-brainer now.

in this decade my worst Linux experience has been attempting to digitally sign a document what a wasteland of decrepit and poorly documented tools