There is a problem with the pdf. Try a new copy, but most likely you'll
need to get the creator to regenerate the pdf.
I've seen this same answer a few times on these forums, but the question is, why does the creation cause these errors and how does the creator avoid them?
According to this thread: http://choorucode.wordpress.com/2010/02/02/adobe-acrobat-embedded-font-error/
the error relates to a font that is used in the document that is incompatible with the version of Adobe Reader being used (or is an outdated font). On the extreme side, the font itself could be corrupted on the PC of the person who created the PDF. So, you'd want to check:
1) Is the font file on the PC corrupted (does this happen only for documents created by one user on one machine)?
2) Is the font outdated/unsupported?
3) Is the font incompatible with your version of Adobe Reader?
There's also the option that the file in question may have been uploaded using FTP in ASCII format, rather than binary.
This was the cause of the issue in my particular case.