How to shrink a PDF

Ghostscript has a handy way to downsizing pdf's if you don't need images and so on at full resolution:

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf

As seen at ubuntugeek.