Debian/Ubuntu repositories have pdftk, which has been good enough for all my PDF merge/split/etc needs. E.g. 'pdftk *.pdf cat output combined.pdf'; 'pdftk -h'

Debian/Ubuntu repositories have pdftk, which has been good enough for all my PDF merge/split/etc needs. E.g. 'pdftk *.pdf cat output combined.pdf'; 'pdftk -h' has more examples