After reducing a PDF's size using Acrobat X the document opens with an error "Cannot find or create the font 'CenturyGothic.'" Some characters may not display or print correctly. Is this normal?

Adobe support indicated to me that this is just a warning error and that the PDF will display correctly and I can ignore this error. I don't like ignoring things though. Is there anything that can be done? Has anyone else seen this error? Thanks