I am currently working on a case where one of my customers who is developing a text from PDFs and sending the PDFs to a NY printing companie. The problem is that when the printing company returns the copies that were made, the Greek fonts (e.g. Ω, µ) do not print out. I checked out the problem, and made a topic of this in the adobe forums but the answers I got back were to try to print out the PDFs in pictures, then make sure the fonts were loaded by pressing Ctrl + F6. I checked my customer's font settings, and the fonts were indeed loaded. FYI: He uses Adobe 7 Pro.

Does the printing company have exactly the same fonts? If not are the fonts embedded in the pdf file? If the customer uses TrueType fonts and the printing company typesetter is set to use Postscript, either the wrong characters will be printed or the quality will be reduced (bitmaps will be used in place of vectors). This is a common problem when the customer uses his favorite font and the typesetter/service bureau/printer either does not have the font or a slightly different version of the font. Helvetica is not Swiss.