This can reduce files to ~15% of their size (2.3M to 345K, in one case) with no obvious degradation of quality.
ghostscript -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/printer -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf
Other options for PDFSETTINGS:
- /screen selects low-resolution output similar to the Acrobat Distiller "Screen Optimized" setting.
- /ebook selects medium-resolution output similar to the Acrobat Distiller "eBook" setting.
- /printer selects output similar to the Acrobat Distiller "Print Optimized" setting.
- /prepress selects output similar to Acrobat Distiller "Prepress Optimized" setting.
- /default selects output intended to be useful across a wide variety of uses, possibly at the expense of a larger output file.
The use of LibreOffice had not occurred to me. MANY THANKS for pointing in that direction. I just reduced a 140MB monster to 6 MB. This was a newsletter with many illustrations. The final result is quite useable on the screen, and will be much easier for the online users to download. The original version (140MB), of course, was sent to the printer for the mailed newsletter.
Getting parameters correct for GhostScript is very frustrating. Glad to see that LibreOffice folks have connected with a good set of tools.