In such case you can use Compress PDF filter which is part of the OS X 10.4; but for the OS X 10.5 Leopard and OS X 10.6 Snow Leopard it must be downloaded and installed since Apple removed it from the OS X.
So, for the OS X 10.5 Leopard Compress PDF workflow can be downloaded from here and for OS X 10.6 Snow Leopard from Apple website.
After you install downloaded package, Compress PDF will appear in the list of available PDF filters.

Another way doesn't require to install anything and based on using Preview and Quartz Composer filter.