I don't know if this is an InDesign thing, or an Acrobat thing, however.. occasionally when I send an Indy ad to Acrobat, I will get anywhere from a couple of letters in a string of copy to the entire line with a white sort of stroke on top. This usually (but not always) happens when there is a stroke around the copy.
Ads are produced in Indesign v5.0.4 on Mac Platform on one of 2 machines (Dual 2Ghz PPC G5, 3Gb RAM, OS 10.4.11 or brand new iMac...).
I use a dedicated PDF server (OS 10.4.11 800Mhz PPC G4 - 1 Gb RAM) with a joboptions folder supplied by head office to produce all pdfs.
I have checked to make sure that colours are all cmyk, yet it occasionally happens. I am using Adobe Distiller Pro, V8.0.0.
This procedure has been bullet-proof for a long time. Anyone have any idea why this would happen occasionally?
Sounds like the document is being "flattened" when made into a pdf. If that is the case and corporate won't allow changes to the pdf settings, then there is no "fix". To avoid flattening of text, make sure it is on the very top and it doesn't have any interaction with other objects (such as transparency or blending effects).
Typically, flattening is used to preserve compatibility with older systems and to avoid font substitutions if the RIP or printer doesn't have a certain font. More modern gear works well with the newer pdf versions and they can see the embedded subset fonts in the file.
"pdf transparency flattening" is a good search term to use to get more information.