Yeah, what Egg points to on the Adobe forum.

Buried in there is the fact that fonts are hinted and that hinting carries through the PDF and the hinting is zoom-level dependent (hinting tries to make fonts look smooth and varies stem thickness according to the point size/zoom levels). Vector graphics are not hinted, which is what text becomes when converted to curves/outlined.

The only real "cure" as mentioned in the thread is to shut off Enhance thin lines in Reader/Acrobat preferences. Do test the printing. The ugly view should not ever print like that. It is a visual oddity on typically vertical and somewhat horizontal strokes and is mostly noticeable in a text run.

Mike