Q:

Open Source command line tool for optimizing PDF

Are there any open-source command line tool for optimizing PDF in Ubuntu. I have used Ghost Script and i am able to convert the PDF into 72 dpi,
gs -sDEVICE=pdfwrite \
   -dCompatibilityLevel=1.4 \
   -dPDFSETTINGS=/screen \
   -dNOPAUSE -dQUIET -dBATCH \
   -sOutputFile=myOutput.pdf myInput.pdf

But what i would like to do is mention what dpi i want to convert the PDF to, like a 300 dpi PDF file to 90 dpi PDF file.

A:

I'll quote zweifel's comment on http://www.ubuntugeek.com/ubuntu-tiphowto-reduce-adobe-acrobat-file-size-from-command-line.html:

dPDFSETTINGS=/screen (screen-view-only quality, 72 dpi images)
dPDFSETTINGS=/ebook (low quality, 150 dpi images)
dPDFSETTINGS=/printer (high quality, 300 dpi images)
dPDFSETTINGS=/prepress (high quality, color preserving, 300 dpi
  imgs)
dPDFSETTINGS=/default (almost identical to /screen)

More options and fine tunning on the site:
  http://milan.kupcevic.net/ghostscript-ps-pdf/

Thus you should use either the option dPDFSETTINGS=/printer or the option dPDFSETTINGS=/prepress to get 300 dpi.

