Hi Eugene, I saw that old article; that's how I found the Steve Werner article. But changing the Flattener presets hasn't had any effect on the export to PDF.

Also – call me stupid, but… I've never had “Composite CMYK” as an option on my Print > Output menu. I'm only able to select RGB and Greyscale. What should I do, to enable CMYK there?

* It's also pretty mystefying to me, because I did large, elaborate books in CS3 for years, and had plenty of CMYK images over a Pantone background, and never had this problem until I upgraded to CS5.