1. A non-transitory computer-readable medium having instructions stored thereon that, when executed by a processor, cause the processor to generate a font for a document, the generating comprising: creating glyph data associated with the font, wherein the glyph data produces a glyph that is displayed within the document; modifying the glyph data, wherein the modified glyph data produces a modified glyph, and wherein the modified glyph is visually substantially identical to the unmodified glyph when displayed within the document; creating a particular character mapping, wherein the character mapping maps a unique character code to the modified glyph; replacing a first instance of a particular character in the document with a first unique character code, wherein the first unique character code is mapped, using the particular character mapping, to a first modified glyph; and replacing a second instance of the particular character in the document with a second unique character code, wherein the second unique character code is mapped, using the particular character mapping, to a second modified glyph.