@figuerres: Seems to (although it's most obvious in the one above that has the large section of bold type font). Interestingly that second PDF causes Firefox to display a banner saying it may not be properly supported. No idea why, it's a bog standard PDF that iirc was generated using Word 2007's built in PDF publisher.

EDIT: Here's another that looks particularly bad.

EDIT: They're fine if you zoom in, but I don't always want to read my PDFs zoomed in.