When you save a file from Adobe Illustrator, you get a choice to "create PDF compatible file" or not. If you don't check that box, what you get is still a PDF file, but it's a thin wrapper around something else, presumably PGF data. It displays in a PDF viewer as a repeated message that it was "saved without PDF content."
Exploring the content of that file with Acrobat Pro appears to tell me that there's nothing in an embedded file or an annotation. I'm trying to figure out where Illustrator is stashing the PGF content. Can anyone enlighten me on this?