I’ve been looking for a decent PDF editor on Linux for years. Like you said, there are plenty that will basically work, but I always have issues with font mishandling.
So far I’ve just settled on using a windows VM with adobe for editing PDFs (along with one other windows only program that I need.) There is a way to get Adobe PDF software working in linux, but I haven’t tried it.
If you need to sign PDFs, xournal++ is an excellent app for applying a saved signature as a stamp.