Linux

I use PDF Arranger a lot for that

https://github.com/pdfarranger/pdfarranger

I use a combination of Okular for signing PDFs and PDF Arranger for rearranging pages, etc

I'd suggest Stirling PDF, just get the Stirling-PDF.jar file from the releases. It does really lots of stuff (though I had some issues with creating pdfs with multiple pages per page). It open a port for the service to run locally and once you close it, it also closes the port.

I also use libre office draw (or firefox printing menu) to create pdfs with multiple pages per page.

There's also xournal as some other people have mention that has some editing capabilities.

https://github.com/Stirling-Tools/Stirling-PDF

I put one in at work. It sat idle for a while until a member of my admin staff asked me how to do a job involving pay slips. We discovered the pipeline tool in Stirling. It is now a permanent system with an SLA!

Each tool has a nice big icon or you can create desktop or browser shortcuts to the ones of interest - ideal for keeping it simple.

As other have said, a combination of Firefox PDF tool, PDF Arranger and Xournal++ is all I've ever needed. And Okular is nowadays my viewer of choice, which does a lot on its own, too.

Don't browsers allow you to do form fillable these days? I swear i just filled one with firefox the other day. Maybe that's too limited?

For combining pdfs, pdftk from the command line is my goto. The command line interface for it isn't too complicated.

https://invent.kde.org/graphics/okular

I like Okular's ability to scan and convert tabled data in PDFs too. There is an option to turn off DRM nonsense. That can do page edits and stuff. If you want to create pages with images you need an office suite.

For "basic edition (rotating pages, etc)", I myself always use pdftk.

"If PDF is electronic paper, then pdftk is an electronic staple-remover, hole-punch, binder, secret-decoder-ring, and X-Ray-glasses."

Xournal++ works pretty good in my experience

I've been through a lot of options trying to get the same functionality you mentioned. I've never found a single app that works particularly well. I'm surprised the state of PDF apps is so poor in Linux. Others have mentioned a bunch of apps and each fails in some major way. I'll come back and check this comment section later for new suggestions for my own sake too.

I like to add xournal++ for editing PDF without a functional form field. And as other said already: PDF Ranger and Firefox itself

For Editing you can use libre office draw or stirling pdf in a docker container. For Formulars and other stuff sounds can use okular.

The options are surprisingly poor.

Personally, I rolled my own TUI script. It uses pdftk to explode and merge, and gs (Ghostscript) to optimize. To paste PNGs of my signature (absurd, but here we are) I use xournal, which looks a bit rough but gets the job done.

This one has a perpetual license option, which could be steep for personal use but could be fine for a business. PDFsam Visual is great for what it does. You can also try it for 14 days too and then decide if it's useful for you or not.

For filling forms mupdf-gl, for combining and rearranging pages pdf arranger, imagemagick to convert images to files (commandline with easy format 'convert file.png file.pdf'), mupdf and zathura to view them.

pdfjam is the only tool i found that resizes images of different sizes to letter size while combining. Though it's cli only. If your file manager has something similiar to Thunars custom actions, you could create little scripts to split, merge, image-to-pdf and put them in the context menu this way.

I've used PDF4QT before.
Didn't get very in depth, but Rotating and Organizing pages worked.

Scribus has really good PDF support. It's a full desktop publishing program (like InDesign), so it might not be the best for quick conversions. It does a really good job of PDF forms though.

Master pdf editor works great for me. License costs $80, but compared to Adobe prices it is basically free.

I'm guessing Firefox's pdf editor is not sophisticated enough

When Python coders create documentation popular options: Sphinx and mkdocs. pandocs for converting a lone vanilla ReStructuredText file.

With Sphinx can create user manual and PDF!

Let me politely add a big warning, there is a learning curve

Any user level questions regarding Sphinx can send my way

Okular for forms. qpdf just for quick viewing and reading. PDF arranger for rearranging pages. pdftk (CLI) for some serious work on PDFs. Exiftool and qpdf (both CLIs) for metadata and linearizing.

LibreOffice has a PDF editor that I use regularly, but its got one big flaw: interpreting word wrap.

Seeing this thread, I'm going to try some of these out.

OnlyOffice is the best I think...