Using GhostScript to compress PDF
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook \
-dNOPAUSE -dBATCH -dColorImageResolution=150 \
-sOutputFile=Journal_Print_LOW.pdf Journal_Print_RAW.pdf
gs -sDEVICE=pdfwrite -dPDFSETTINGS=/prepress -dNOPAUSE -dQUIET -dBATCH \ -sOutputFile=Journal_Print_HIGH.pdf Journal_Print_RAW.pdf