Nothing Was Delivered

Nifty trick and saved my bacon today. 

Long story short, Preview in Lion (and also, I’m assuming, Mountain Lion) lets you chose File -> Export. Towards the bottom of the Save screen, you’ll see the option for Quartz Filters. Choose Reduce File Size. If the resulting PDF compresses your images too much, you can create a custom filter with OS X’s Color Sync app. 

Then to use this new filter just right click on the PDF you want to compress, choose Open With -> Color Sync, pick the filter you want, and hit Apply.