Compress pdf using Ubuntu / Reduce file size

150dpi images

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

gs switches: http://milan.kupcevic.net/ghostscript-ps-pdf/