• Easy way to concatenate PDF files in Ubuntu Linux | Doei Doei
  gs -q -sPAPERSIZE=letter -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=output.pdf file1.pdf file2.pdf file3.pdf [...] lastfile.pdf
  in GNU/Linux with batch command gs line pdf pdfwrite

pdfwrite from all users