Make pdf document smaller, Mac and Linux

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -dNOPAUSE -dQUIET -dBATCH -sOutputFile=name-of-output-file.pdf inputfilename.pdf

Other options for dPDFSETTINGS=/screen
/printer
/ebook
/default