In addition to using Unicode characters for entering special characters, you can also overscore text, underscore text, or insert a special character by including control information in the text string. Use a pair of percent signs to introduce each control sequence.
You can use this control code with standard AutoCAD text fonts and Adobe PostScript fonts.
The following options are displayed.
Draws a single percent sign (%). This is valid for the TEXT command only.

Overscoring and underscoring can be in effect at the same time. Both turn off automatically at the end of the text string.

You can use the %%nnn control sequence to display special characters using the PostScript fonts.
A sample drawing (truetype.dwg) showing the character map for each font is provided in the sample folder.