When exporting to PDF or to graphics files you can apply a filter to the process. This allows for various adjustments to be made as the file is saved. It is even possible to create your own custom filters for tailor made results.
To choose a filter click the filter popup button and select an option from the menu. To create a custom filter select the Add Filters command. This will open the ColorSync Utility. Here you can add and set-up a filter. When you are done and quit the ColorSync Utility the popup will list the new filter under the Your Filters heading.
Note: Note that you can make a Generic PDFX-3 document by applying the aptly named system provided filter for that purpose.
Another popular filter is the Reduce File Size filter, which will attempt to reduce the size of bitmapped graphics in your document. The result of the Reduce File Size filter will vary depending on how many bitmapped graphics are in the document, and on how much reduction is feasible.