I don't see a problem with it if the translation is 1-to-1 (and that's a pretty big if). Disregarding federal law for the moment, what is the harm in the mailman reprinting your letters with nicer font on nicer paper? It seems to me that if the mailman wants to do that, as long as they don't lose any of the information of the original letter I would benefit from having an easier to read letter.