(These programs, mentioned below, allow reordering, deleting, rotating, pages in pdf files, and merging pdf files together)
PDF Slicer a good replacement for PDFmod, PDF Shuffler, or PDF Arranger - which aren't available as an appimage, flatpak, or snap (I don't get on well with PDF Sam in the Solus repo).
I had bother with PDF Slicer when trying to open files, but installing xdg-desktop-portal-gtk
solved it.
Info was found here.
So here's how to install it and avoid bumping into that:
PDF Slicer on Solus
https://junrrein.github.io/pdfslicer/
sudo eopkg install flatpak xdg-desktop-portal-gtk
flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
Restart the system
Go to: https://flathub.org/apps/details/com.github.junrrein.PDFSlicer
Click Install on the site, and save the file: com.github.junrrein.PDFSlicer.flatpakref
In your terminal go to the location of the downloaded file
Run: flatpak install com.github.junrrein.PDFSlicer.flatpakref
That's it, you should be good to run PDF Slicer from your main menu