How to compress a PDF on a Mac without Acrobat

To compress a PDF on Mac that does not have Adobe Acrobat, open the PDF in Preview. Then go to File > Save as. (Warning: If you go to File > Save, you will over-right your original high quality PDF file.)

From the Quartz Filter option menu, choose "Reduce File Size" and save a new copy of the PDF.
(This option will compress the images to produce a smaller PDF file.)

The new copy of the PDF should have a much smaller file size that is more useful for quick web viewing. I was able to reduce a 7.2 MB PDF that included several images into a 252 KB PDF file using this feature of the Preview application.