How can I combine multiple PDFs using the command line?

Is there a quick one-liner to combine multiple pdfs into one?

I know it can be done using Preview.app

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