What indicates that the font is embedded in the PDF file?

Question

My problem is the following: I have a PDF file, and I check for numerous things about its text, pictures, etc. But I still can't manage to find an answer how to figure it out, if the actual font, which is used is embedded or not. What indicates it in a PDF file? How are the extractors, or the PDF readers checking it? (Since they can tell in the properties of the file that it has xy embedded fonts.)

Any help or tip would be much appreciated, since I am getting lost in between these PDF technology pages without any luck.

Answer 1

Every font in the PDF file (except base 14 fonts) must have a FontDescriptor dictionary. This dict contains a lot of information about the font, and amongst other things can contain keys that contain embedded font files ("FontFile", "FontFile2" and "FontFile3"). The presence of these keys indicates whether the font is embedded or not.