No need to upgarde. You do this by setting up the field to allow for rich text formatting. See the Options tab of the field properties dialog for this option.
Note that the user will have to know how to select a font. It's not immediately apparent how to do this, so you should inform your users how to bring up the Properties bar by pressing Ctrl+E, or cmd+E on the Mac. When a field that allows rich text formatting has the focus, the Properties bar will allow them to choose a font.