Gs

Reduce PDF file size to 150 dpi images for reading on a e-book device
gs -dNOPAUSE -dQUIET -dBATCH -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -sOutputFile=dune.pdf Dune_Encyclopedia.pdf

Extract pages from a PDF file
gs -sDEVICE=pdfwrite -dNOPAUSE -dBATCH -dSAFER -dFirstPage=34 -dLastPage=34 -sOutputFile=test2.pdf The-Cambridge-Handbook-of-Physics-Formulas.pdf