Built-in Google Viewer - How do I disable full screen mode?

I am using Google Viewer as an embedded PDF-Viewer in a web app (PhoneGap). My problem is that when I open a PDF on iPad and go to full screen, there is no more option to go back because there is no "back" button on Android devices. Therefore, I would like to disable this setting in order to access full screen mode.

This is my code:

        <iframe 
            src="http://docs.google.com/viewer?url=http://www.physik.uni-wuerzburg.de/fileadmin/tp3/ThermoEDynamik/Uebungen/aufgabe29_31.pdf&embedded=true" 
            width="750" 
            height="1125" 
            style="border: none">
        </iframe>

      

        
        
        
      

    

I thought there should be an option like width and height for full screen.

Thank you for your help!