sometimes large size PDFs need to be optimized for email or other purpose.
There is a option called optimizers in adobe acrobat, but it doesnot always give desirable results.
Here PDF Shrink comes handy. it does above job flawlessly, within minutes.
it also has templates for PDF shrinking purpose.
download from their site.
this works for version 4.5.3, running on mac os lion 10.7.1
and, always use little snitch (http://www.obdev.at/products/littlesnitch/index.html) to block application calling home.