Apple - How can I combine multiple PDFs using the command line?

Have a look at "Combining PDF files on the command line in OSX" in Joining PDF Files in OS X From the Command Line.

It turns out that from Tiger onwards, OSX ships with a Python script that does exactly what you need. The script is already executable, and Python is pre-installed on OS X, so all you need to do to run it is opening the Terminal and typing

"/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

Also on the linked page it suggests making a symbolic link for the join.py file to make typing easier however they omitted the -s in ln -s ... ..., and without it, a hard link is created. Probably wouldn't matter, however though I'd mention it.

Just install Ghostscript using Brew with command:

brew install gs

Then run command with all files listed:

gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=merged.pdf source1.pdf source2.pdf source3.pdf

I found the free Coherent PDF Command Line Tool to be the best option. It is very fast, lossless, and does not mess up orientation or hyperlinks as some other solutions did. Format is:

cpdf file1.pdf file2.pdf -o output.pdf