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.
@cschwaderer Any processing (modification) will always invalidate digital signatures, that is a principle of digital signatures. I.e. even if they were left in the document (and not removed by ghostscript), the signatures would no longer match with the changed document. That is correct, since the signer did not sign the changed (processed) document, only the original one.