Compress PDF and Merge PDF are fantastically easy to use. I would highly recommend them had it not been because I cannot guarantee who has access to the data.
So is there free (as in freedom) software that I can install, which does the same?
I know of PDFTK, but I am interested in a web frontend similar to the above (Linux or Windows is fine), or at the very least a free (as in freedom) software Windows tool that is just as easy to use.
Note: My users are naïve Microsoft Windows users. So cmdline for Linux is unfortunately not usable.