A character set merely selects which set of glyphs (character shapes) matches the 8-bit character codes used to select the required characters; this is because a font may contain many more than the (maximum) 256 characters addressable by an 8-bit character code..
It has nothing to do with the design (shape) of the glyphs themselves - this is defined by the typeface (sometimes mistakenly referred to as the font) and other attributes (style (upright, italic. etc.); weight (normal; bold; etc.); size; quality).
I've no personal knowledge of dot matrix printers - as far as I can see, your specification document doesn't mention typefaces or fonts, so it may be that you have only the one typeface design available (although perhaps in different size, style and quality variants).
You'd need to find a User Guide, or Programming Guide document for the printer in question to find out how (if at all) you can influence the output design/quality.
