Small tool to merge or split PDF files on the command line
You need the opam package manager, a recent version of OCaml, and the dune build system installed on your machine. Install the camlpdf package with opam install camlpdf. Run dune build main.exe and you will get the executable in _build/default/main.exe.
main.exe a.pdf 1:2:4 b.pdf : takes pages 1, 2, 4 from a.pdf to b.pdf.
main.exe a.pdf 1:5-8 b.pdf : takes pages 1, 5, 6, 7, 8 from a.pdf to b.pdf.
main.exe a.pdf 4- b.pdf : takes all the pages counting from page 4 (included) in a.pdf to b.pdf.
main.exe a.pdf -7 b.pdf : takes all the pages before page 7 (included) in a.pdf to b.pdf.
main.exe a.pdf 1:5 b.pdf -3:6:8-10:12- c.pdf : takes pages 1 and 5 from a.pdf, pages 1, 2, 3, 6, 8, 9, 10, and all the pages after 12 in b.pdf, saves in c.pdf.