https://apple.stackexchange.com/questions/230437/how-can-i-combine-multiple-pdfs-using-the-command-line
"/System/Library/Automator/Combine PDF Pages.action/Contents/Resources/join.py" -o PATH/TO/YOUR/MERGED/FILE.pdf /PATH/TO/ORIGINAL/1.pdf /PATH/TO/ANOTHER/2.pdf /PATH/TO/A/WHOLE/DIR/*.pdf