Ghostscript oneliners
merge multiple PDFS using ghostscript
https://gist.github.com/brenopolanski/2ae13095ed7e865b60f5 :
A simple Ghostscript command to merge two PDFs in a single file is shown below:
gs -dNOPAUSE -sDEVICE=pdfwrite -sOUTPUTFILE=combine.pdf -dBATCH 1.pdf 2.pdf