You may not be able to shrink down the document as much as you need but it's worth a try: With Adobe Acrobat (this will not work in the free Reader), select Tools>Document Processing>Optimize scanned PDF, then select to use adaptive compression and pull the size slider all the way to the small size end.
Karl Heinz Kremer
PDF Acrobatics Without a Net
PDF Software Development, Training and More...
http://www.khkonsulting.com