Unfortunately not open source, but I have good experience with Master pdf Editor. It "is a proprietary application to edit PDF documents on Linux, Windows and macOS. It can create, edit (insert text or images), annotate, view, encrypt, and sign PDF documents.": https://www.linuxuprising.com/2019/04/download-master-pdf-editor-4-for-linux.html
Unfortunately I didn't find any single PDF editing app that stands out, so far. Although it's important to note that Firefox as made some progress recently on this topic. The embedded PDF viewer now allows to write, sketch and draw on documents (e.g a signature) and save the changes, i think you can also highlight. When it comes to digital signatures and adding/removing/sorting pages, you will need another app.
What are you doing with it? Okular is a nice FOSS solution for viewing, annotating, signing, etc. which covers many people's usage. If you really need a full editor, I would generally stick with Adobe's stuff. Don't know any free or FOSS solution that works better.
Thanks. Yeah, I’ve started to check out Okular, but I think it doesn’t allow you to change the pages. So maybe a combination of the two would fulfill my requirements.
I'm using pdftk to add/remove pages, which works perfectly. Also does stuff like rotate some pages, ect. Easily scriptable, so stapling together all the PDFs in a dictionary is super easy.
For actual editing (removing text, adding complex things), I just use Inkscape. How well that works depends on the PDF itself.
And just highlighting text is something every single PDF viewer can do nowadays.
To the best of my knowledge, there isn't a good FOSS PDF editor.
There's LibreOffice Draw, but as you said, it messes up the formatting. There's also Inkscape, but good luck if you have pages of text.
You can also try Scribus, but I wouldn't say it's good (or intuitive).
If all you want to do is write over a PDF, put (not edit, nor remove) text, formulae, or images, then Xournal++ is very decent.
If I need to edit a PDF, I use (*gags*) Adobe Acrobat running in Wine (with Lutris is very easy). It's as proprietary and evil as it can be, but it's good at editing PDFs.