How to display preview of any data from iPad on external monitor?
You can give Keynote for iPad a try.

You can put all the presentation content in a keynote file (PDF, images, videos), start the presentation from Keynote from iPad app, display the presentation on an externally connected monitor while still working on something else on your iPad. The iPad app acts as the remote for controlling the presentation while you can also use your iPad for other tasks.


Keynote for iPad: Play a presentation on a separate display