Answered
My file is created in pdf version 1.4, and when I try to Optimize (or reduce file size in any other way), some of the fill colors go away - but not all of them. The page headers are black fill with white text, and some of the black fill goes away when optimizing, just not in all areas. When I try to edit the text I can see that it still exists, but just isn't visible without the black fill. I've looked for all kinds of settings, but since not all of areas with the fill are removed I'm at a loss.
What other ways have you tried to reduce file size?