For Type1Fonts, if four .afm files are supplied the
  fifth is taken to be "Symbol.afm".  Relative paths are taken
  relative to the directory R_HOME/library/grDevices/afm.
  The fifth (symbol) font must be in AdobeSym encoding.
  However, the glyphs in the first four fonts are referenced by name
  and any encoding given within the .afm files is not used.  The .afm files may be compressed with (or without) final
  extension .gz: the files which ship with R are installed as
  compressed files with this extension.
  Glyphs in CID-keyed fonts are accessed by ID (number) and not by name.
  The CMap file maps encoded strings (usually in a MBCS) to IDs, so
  cmap and cmapEncoding specifications must match.  There
  are no real bold or italic versions of CID fonts (bold/italic were
  very rarely used in traditional East Asian topography), and for the
  pdf device all four font faces will be identical.
  However, for the postscript device, bold and italic (and
  bold italic) are emulated.
  CID-keyed fonts are intended only for use for the glyphs of East Asian
  languages, which are all monospaced and are all treated as filling the
  same bounding box.  (Thus plotmath will work with such
  characters, but the spacing will be less carefully controlled than
  with Western glyphs.)  The CID-keyed fonts do contain other
  characters, including a Latin alphabet: non-East-Asian glyphs are
  regarded as monospaced with half the width of East Asian glyphs.  This
  is often the case, but sometimes Latin glyphs designed for
  proportional spacing are used (and may look odd).  We strongly
  recommend that CID-keyed fonts are only used for East Asian
  glyphs.