I love PDFArranger. It has basic functions such as rotate, add or delete pages and it comes very handy for large documents. Also It is available on Linux, Mac and Windows: https://github.com/pdfarranger/pdfarranger
I have tried to install it on my pi4 as well but it craps out when doing simple stuff... Maybe it's because I have out it behind nginx as a reverse proxy... I'll try again when I have time, because it works very well (when it works).
I use command line tools for this, for most those things pdftk should be enough and it works great -if the command line is too daunting for you, there's PDF chain a graphical front-end for pdftk.
For creating PDFs from images i often use imagemagick.
I have been looking for an open source editor that is comparable to Acrobat Pro for years. In fact, this and that it is not even acknowledged that such an essential tool for office workers is missing in Linux are among the main reasons I don't ditch Windows on my main machine.
PDF Arranger, Ghostscript and Master PDF are indeed useful.
PDF4QT was not mentioned by others. It works well already and is a very promising PDF viewer, organiser, editor. I am not sure why it has to be split into three applications.
qpdf is the best CLI tool that I have used to edit the structure of a PDF. I recommend it if you don't require a GUI, and do not need to edit the content.