I have received a pdf made in Quark 9.3.It is to be printed on uncoated paper so I have to take down the total ink coverage to acceptable levels. I do this using Color Convert in Acrobat (10.1.9), it is an operation I do several times per day and has been doing for years without problems, but of course the overwhelming majority were med by InDesign. But this time… When converting colors it removes shadows, and on a picture of a white snowflake on magenta background the background gets 40% cyan where there previously were none. It really destroys the original like I have never seen before. Looks like a bug to me. Is this "a well-known error"?