Thanks for your reply Petya,
For the most part you are right. It is theoretically possible using that code. However there is a problem: The text box that is inserted in the page using this method, never receives the keyboard focus and therefore user cannot enter anything in it.
This is how I did it: In the code that you mentioned, I added the following code snippet inside HighlightUILayer.cs in the Initialize function so that a text box appears on the top left side of each page:
Width = 200,
Height = 30,
Do you think this is solvable?