[Geoff Bacon]

A quick popup near the bottom right would probably work (as this is where the "performance mode" is enabled). The user is probably immediately concentrating on the top of the screen so it would be out of the way.

Having said that, detecting the clicks and displaying a quick popup in the middle of the screen would probably be better; when a user has tapped several times it probably mans they want to edit (if they are trying to change pages then they are not interested in this page anyway). I suggest a "disappearing" transparent popup rather than a dialog that requires a response.

I don't think you need both of the above.

As McAroni says, after you have experienced this a few times, you can make a good guess at why you can't get overlay mode. However, beginners tend to select options to "see what they do" and it is quite easy to leave it set because nothing instant happens on the screen. The problem happens later because they don't remember that they have selected this mode.

I agree with Skip that it would be better to say "editing" rather than "overlay" but this might not help the user find the correct place in the manual (for those who might read it!)

Cheers
Geoff