PCL font selection sequences - are a series of parameters that are used to specify what font will be used to display a particular character code. The shape of each character (the glyph) in a font depends on the the style (italic, bold etc.) and the typeface (Courier, Arial etc.). The character code that is used to display a particular gylph depends or the Symbol Set used in the selection sequence.
Other parameters are used specifiy weight size and pitch. When a particular parameter is omitted then a printer default may be used. This may mean a different font is substituted.
PCL Printer Drivers may download a sub-set of a particular font so that the correct characters are available, or convert "difficult" characters to raster image data. RedTitan EscapeE will extract and install font sub-sets as required and decode character code positions by analysing installed fonts.
Converting PCL to PDF introduces a number of other font selection issues. You can limit PDF file size by using fonts that are always available in ADOBE READER. The Adobe 13 standard fonts are regular, bold, italic, and bold-italic variants of Times, Courier, Helvetica, and the Symbol font.