code: @Nonnull
    public PDFont loadPDFont (@Nonnull final PDDocument aDoc) throws IOException
    {
      if (m_aFont != null)
      {
        // Pre-defined font
        return m_aFont;
      }
  
      PDFont ret = null;
      if (m_aTTF != null)
        ret = PDType0Font.load (aDoc, m_aTTF, m_bEmbed);
      else
        if (m_aOTF != null)
          ret = PDType0Font.load (aDoc, m_aOTF, m_bEmbed);
  
      if (ret == null)
        throw new IllegalArgumentException ("Cannot load font resources of type " + m_aFontRes.getFontType ());
      return ret;
    }
docs: Load the {@link PDFont} associated to this preload font. This class uses no
  caching!
  
  @param aDoc
  The {@link PDDocument} to which the font should be attached to. May
  not be <code>null</code>.
  @return The loaded font.
  @throws IOException
  In case loading the external file fails