I guess you all know you can reduce the size of a PDF on a Mac via “Save as …” in Preview and then selecting “Reduce file size” as the Quartz filter. The problem with this filter is that it often degrades the image quality to an unusable degree. You can create your own Quartz filter that uses more adequate compression settings.

I was very satisfied with these settings:

• Image sampling: set resolution to 96 dpi and nothing else
• Image compression: medium JPEG compression

This shrank a photominutes PDF from 35 to 1.6 MB with hardly any visible loss of quality.