Alfred Klomp's script for resizing pdfs (source: http://www.alfredklomp.com/programming/shrinkpdf/).
Usage excerpt from the site:
You can also provide a second filename for the output:
./shrinkpdf.sh in.pdf out.pdf
And an output resolution in DPI (default is 72 DPI):
./shrinkpdf.sh in.pdf out.pdf 90