Post date: Oct 13, 2011 8:37:10 PM
Compressing a PDF file
Large PDF files can be difficult to archive or email. Using Preview, you can compress a PDF file so it’s easier to share or store.
This process compresses the images in the file. The compressed images look the same as the originals when viewed onscreen, but may appear to be of lower quality when printed.
From: Mac tip http://docs.info.apple.com/article.html?path=Mac/10.5/en/9021.html