bash split pdf

$ sudo apt-get update
$ sudo apt-get install pdftk

EDIT: since pdftk became deprecated, do:

sudo snap install pdftk

Then, to make a new pdf with just pages 1, 2, 4, and 5 from the old pdf, do this:

$ pdftk myoldfile.pdf cat 1 2 4 5 output mynewfile.pdf

Note that cat and output are special pdftk keywords. cat specifies the operation to perform on the input file. output signals that what follows is the name of the output pdf file.
You can specify page ranges like this:

$ pdftk myoldfile.pdf cat 1-2 4-5 output mynewfile.pdf 

http://linuxcommando.blogspot.ca/2013/02/splitting-up-is-easy-for-pdf-file.html