Thanks for the reply.
I don't see a "smooth text and line art" option in my Preview. I went and changed the 1 point equals 1 screen pixel option. It made no difference.
I fired up TextEdit in OS X and just put in some text and saved it out as a PDF, then opened it in Preview and Acrobat. The same result – Preview's text is bolder than it actually is, and a little fuzzy. Screenshots attached.
Preview:
Acrobat:
From Illustrator – Preview:
From Illustrator – Acrobat:
There is a clear bolding of the text in Preview.
And what's weird is if I take the same PDF and bring it into Apple's Keynote, the PDF is rendered correctly. It's only in Preview I'm having an issue.