====Merge====
  pdfunite in01.pdf in02.pdf in03.pdf out.pdf

====Resize====
  gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf

in dPDFSETTINGS : screen, ebook, prepress, printer

====Print booklet====
  * 4 page booklet: Type 4,1,2,3
  * 8 page booklet: Type 8,1,2,7,6,3,4,5
  * 12 page booklet: Type 12,1,2,11,10,3,4,9,8,5,6,7
  * 16 page booklet: Type 16,1,2,15,14,3,4,13,12,5,6,11,10,7,8,9
  * 20 page booklet: Type 20,1,2,19,18,3,4,17,16,5,6,15,14,7,8,13,12,9,10,11