Prepare a font for later use with
pdf_setfont(). The metrics will be loaded, and if
embed is nonzero, the font file will be checked, but not yet
used. encoding is one of
"builtin", "macroman", "winansi", "host", or a user-defined
encoding name, or the name of a CMap.
pdf_findfont() returns a font
handle or FALSE on
error.