pdfslicer VS pdfarranger

They don't have to be! PDF Arranger or PDF Slicer will do this for you much more easily than PDFsam would:

https://github.com/pdfarranger/pdfarranger

https://github.com/junrrein/pdfslicer

If you just want to add another page I recommend to use another tool like PDFSlicer or PDFArranger.

You could also look at how other people and organizations have implemented GitHub Pages in their projects. For example, PDF Slicer has a master branch which houses the code for their application, and a gh-pages branch which houses the code that produces the documentation website. You can also have a repository/branch that exists solely to create a GitHub Pages website like this Picross page.

On Linux I like to use:

https://github.com/pdfarranger/pdfarranger and https://gitlab.com/scarpetta/pdfmixtool for such tasks.

Für PDFs verwende ich pdfarranger.

I see some questions in the comments about document splitting and if you are using PDF for the export in scanning, this adds an extra step but may be valuable in the long run. For Linux users at least, there is "pdfarranger" which most distros have. You can install that, load the PDF and re-arrange pages, remove pages, etc.

PDFArranger

So, I guess, pdfarranger might be faster than PDFSam. https://github.com/pdfarranger/pdfarranger

I like PDF Arranger for converting JPEGs to PDFs (open source on Windows) https://github.com/pdfarranger/pdfarranger.

I have always only been using PDF Arranger for manipulating PDF files (merging different files, arranging, adding, deleting pages) and I'm wondering if there really is no KDE equivalent for that application.