This command line combines file1.pdf with file2.pdf, to create finished.pdf. One additional bonus is that if files 1 and 2 weren’t compressed properly, the final finished file will be and it’s always nice to save disk space.
gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=finished.pdf file1.pdf file2.pdf
kthxbie