It is possible to do it in python. you would just need to create a text box in the MXD and type in the note that you wish to add to the map. Place the note in the location you wish to place it on. Now Right click on the text box and go to the Properties>Size and Position tab. Under element name give it a name, in your case say call it Note and make a note of he XY position of it and move it somewhere off your layout view.
Now via python you can access this element and have a trigger, say for example when page name from your DPP = page 5 then set text box position equal to the position noted above and once you are off that page, set the text box position to something out of your layout view.
