If you are interested in merging multiple pdf files together, extracting single pdf pages from a larger document or reorder a pages, “pdftk” makes the life pretty easy!
Simply install it (“sudo apt-get install pdftk” in ubuntu/debian based distros) and then use it as follows:
to explode one big pdf into unitary pages:
pdftk <path_to_pdf_file> burst
This will generate pg_00n.pdf single files in current directory from which command line is being executed.
to merge multiple pdf files together: put them all into a given folder and run:
pdftk <path_to_pdfs>/*.pdf cat output output.pdf