Concatenating PDF files using ghostscript
If you ever find yourself with multiple PDF files that need to be combined into one single PDF you can use the following incantation on Linux:
gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=finished.pdf file1.pdf file2.pdf
Using ghostscript the input files are
file2.pdf with the joined file ending up in finished.pdf.