I'm using Aacad 2004. This comes with Express tools which has a feature to do this. From the Express menu choose "Text" and then "Arc-Aligned Text". It's pretty self-explanatory.
If you don't have Express tools, your on your own. Sorry.
If you dont have the express package the only possible way I can think of to do arc aligned text would be a "manual" sort of way. That is to write each letter as an individual text and the use the rotate command to rotate each letter separatly, This would take a hell of a long time-but if it's that important it might be worth considering.
With gpavlab recommendation, make sure to generate an arc
subdivided with equal radial lines, then the letters can be equally spaced at the intersections of the arc and radial lines in order to get a uniform presentation. The degrees of rotation the letters can be determined from the angular positions of the radial lines. Invoke the LI command on the radial lines for their angular positions.
