Master PDF Editor is one of two proprietary apps I currently have running on my laptop, and I would definitely say it's worth the price (although once in a while when they update they manage to mess something up, but will usually get around to fixing it eventually).

This was quite a long time ago, but I had a lot of issues with Okular, though I don't remember what exactly (one thing was that if you changed a document's location, Okular would lose all the bookmarks you added to it, but they may have changed it since then, IDK). Evince's commenting features seem a bit rudimentary to me, but I've only used the one from the Mint repo, so there may be a newer version that's better.

There's also PDF4QT which is open source, but is kind of new and may be a bit buggy.

Adobe used to make a linux version of acrobat reader that will probably do the trick. You're not going to find it on adobe's download site, but it is still there at the link this tutorial uses. I just checked.

Not what you are looking for... but I work in print and often need to edit pdfs in a much more base level. Inkscape can be a pretty powerful program for that.

'PDF Arranger' is a good program if all you need to do is rearrange or combine pages in one or more pdf files.

Okular is the way to go for anything that's typed, it has a lot more capabilities than Evince. For handwriting, I've used Inkscape, and Libreoffice Draw. They're roughly similar in capabilities.

Zathura

stirling pdf is self hostable i run a instance

If the reports are somewhat technical (written with Latex for example), check out sioyek: https://sioyek.info/. It's a PDF reader mainly for academic use.

Sioyek has made reading and reviewing papers SO much easier and it's really, really convenient... once you get the hang of it. It takes a bit of time to get used to all the things, but it's worth it. I also review students' theses with it. Highlighting colors and adding comments is super easy (select text, h+g (green highlight), type comment).

If you have want to export your notes and comments, you will need this script though: https://github.com/ahrm/sioyek/blob/main/scripts/embedded_annotations.py

If you need advanced modifications, Inkscape is surprisingly capable!

If you need more than just basic annotations, you can edit PDFs with LibreOffice Draw. PDFs aren't intended to be editable, so nothing is going to be like editing the original document unless the PDF was created with LibreOffice and exported as a hybrid PDF.

Atril and xpdf don't have any markup capabilities, but Okular has. You can install Okular regardless of what desktop environment you are using.

Firefox has become great for simple forms and annotations. I used to dick around with libre draw or inkscape or such but I generally just need to add some text or check a box and firefox does that about as well as anything else even on a photo type pdf.

xournal is nice for handwriting on pdfs. I use it with a Wacom tablet which has first-class Linux kernel driver support.

Zotero. Syncs even between different devices. Bibliography and annotation. Great.

I'm still using good ol' Xournal. It isn't really particularly good (and I'd be happy to find something better), but I've been using it since forever and the force of habit is strong.

https://en.wikipedia.org/wiki/Xournal

Firefox (yep, the browser)

As someone said, Evince under Gnome/GTK. Okular in KDE is pretty capable, as I understand. Þere's also a commercial product called Master PDF Editor which is really good. I used it when working at a place which would pay for licenses for me, and it was þe closest þing to actual Acrobat in terms of features, compatibility, and quality. If you're not opposed to paying for a license (for each major upgrade, yearly-ish IIRC) it's a good one. You can also trial it.

Firefox is able to do this for basic PDF annotations. It's not very extensive, but it's very simple to use (and you probably already have it installed).

Papers or Zathura (+ required plugin)

Try evince.