How can I determine if a glyph is missing in an embedded font?

Q: I have PDF file where the mebedded font does not include all
requred glyphs.

The “ ’ ” character is not embedded with the rest of the font. So the
font results as embedded, but really the character “ ‘ “ is not

How could I traverse every character in a text checking if every
character is really included in that font? Because the subset
sometimes doesn’t include only a few characters.
A: You could traverse all characters in a text run using
pdftron.PDF.CharIterator (as shown in ElementReaderAdv). You can pass
itr.Current().char_code to font.GetGlyphPath() and if the method
returns false it means that the embedded font is missing a glyph (if
the font is missing you with get a substituted path).