To reduce size of a pdf it is possible to use ghostscript command:
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook \
-dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf-PDFSETTINGS=configuration:
- -dPDFSETTINGS=/screen lower quality, smaller size (72 dpi)
- -dPDFSETTINGS=/ebook medium-resolution quality (150 dpi)
- -dPDFSETTINGS=/printer print optimized quality (300 dpi)
- -dPDFSETTINGS=/prepress prepress optimized quality
- -dPDFSETTINGS=/default intended to be usefull across a wide variety of uses, at a larger output file