Hi Kim,
We have a knowledge base page that covers the tricks we have so far.
Color Render: Excessively Large File Size or Gradient Issue
The biggest one is usually if there's a lot of gradient hatches in the file. You can change those to solid colour hatches. We've just recently added a lot of new solid colour options to help with this.
If you're using no gradients and still having a file size and printer issue, we've found that for PDF's with a very large number of solid hatches (or colour tree symbols use solid hatches as well), vector PDF's have performance issues. It's a problem with the file type itself handling vector-based solid hatches. Take the PDF into Photoshop instead or another program that will help you transform the PDF into a raster-based file instead. The file size might get bigger than it was before but printers will be able to handle that file better than a vector pdf with vector solid hatches.
We haven't yet heard of a way to output raster PDF's directly from AutoCAD or F/X CAD.
-Amanda