I need to lower the size of a pdf file from 250 Kb to 150 KB without damaging the electronic signature.
Then it comes down to which signature is on it. Open the file in Acrobat Reader and click the signature box:
- If it says 'Signed by ...' with a valid check, that's a cryptographic signature. It locks the exact bytes of the file. Any recompression invalidates it: Acrobat 'Reduce File Size', Ghostscript, qpdf, pdfsizeopt, all of them. There is no honest way to shrink it and keep that signature. Options: keep the 250 KB as the signed master and send a smaller unsigned copy, ask the signer to re-sign the smaller file, or replace the 150 KB cap with a link.
- If it's just a picture of a signature on the page (no certificate), shrink freely:
gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -dNOPAUSE -dBATCH -sOutputFile=small.pdf in.pdf
/ebook downsamples images to ~150 dpi; /screen goes smaller. Eyeball it before you send.
What is the 150 KB for, an upload form? That changes which path is right.
- If it says 'Signed by ...' with a valid check, that's a cryptographic signature. It locks the exact bytes of the file. Any recompression invalidates it: Acrobat 'Reduce File Size', Ghostscript, qpdf, pdfsizeopt, all of them. There is no honest way to shrink it and keep that signature. Options: keep the 250 KB as the signed master and send a smaller unsigned copy, ask the signer to re-sign the smaller file, or replace the 150 KB cap with a link.
- If it's just a picture of a signature on the page (no certificate), shrink freely:
gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -dNOPAUSE -dBATCH -sOutputFile=small.pdf in.pdf
/ebook downsamples images to ~150 dpi; /screen goes smaller. Eyeball it before you send.
What is the 150 KB for, an upload form? That changes which path is right.
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