Just a quick one, as I now needed this for the second time and already didn't write it down the first time …
I found this when looking for a way to combine multiple PDF documents into one. You just need to
sudo apt-get install gs pdftk
- gs -dNOPAUSE -sDEVICE=pdfwrite -sOUTPUTFILE=combinedpdf.pdf -dBATCH 1.pdf 2.pdf 3.pdf
Pretty self explaining, so I'm gonna end early here.