From the Font option in the Character menu of the help editor/viewer or the built-in text editor, you can specify the font and text attributes to use in the text buffer. This will bring up the Windows standard Font dialog box where you can specify a new font name and character style, size or color.
Note that ATPDraw does not remember the current font setting when you terminate the program, so if you don't want to use the default font, you have to specify a new one each time you start ATPDraw.
Component Labels and Node Names follow this font. The Text can have their own fonts which is stored in the project. See the Open Text dialog.