[desmap]

Something I still miss is a free and easy PDF tool which lets you delete, reorder and add pages from multiple PDFs. On Windows there is just Xodo but its UX is unfortunately subpar and on macOS you have Preview where the UI is better but once you have multiple PDFs from where you get the pages it can get confusing.

[c-st]

On Linux there is https://github.com/pdfarranger/pdfarranger It has a nice UI and is pretty easy to use.

[karthickgururaj]

PdfTk does this. I use the CLI version, but I think there is one with a GUI as well.

[hnick]

pdftk is by far my favourite for this too. It's quite fast but it does run into some file size problems when merging files as it doesn't deduplicate resources, and can crash outright on some bigger files.

[number6]

On Windows there ist: https://www.pdf24.org/