Hi Lisa,
I tried to find out more on this but other than the suggestions I made in your other thread, I could not find a solution using Acrobat or Reader. If this is only happening with one PDF file or only PDF files from one source (author) then it is probably a problem with how the file was rendered in the first place.
Hope this helps,
Dimitri
WindJack Solutions
www.windjack.com
www.pdfscripting.com