To reduce the size of a PDF, you may try run this command on a linux box:

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

If the -dPDFSETTINGS=/ebook option produces too pixeled pictures, try -dPDFSETTINGS=/prepress, if you need an even smaller file size, try -dPDFSETTINGS=/screen.