What is PDFNet doing when font is not present (embedded) in the document?

Q: What PDFNET is going to do if the font used for a text (used for
form processing) is not present, may be embedded in the PDF itself, on
the system where the application is running?

A: If the font is embedded PDFNet will use the embedded font. If the
font is not embedded PDFNet will search system fonts for a match. If
the exact match is not fond a substitute font will be selected. The
font substitute rules are fairly complicated and are evolving. PDFNet
also lets you to override the default font substitution behavior using
PDFNet.AddFontSubst() for specific font instances or specific classes
of fonts.