Hi everyone, i am going to write about my ideas of how i think this feature would work for me if i was using it for notation and perhaps other things as well but still keeping it work well with the existing ST3 interface which we love so much.
I will look at this feature from an on stage perspective and with the Ipad 1 meter away so it does not obstruct the performer from an audience point of view.

These are the main needs i would expect.

The ability to treat the PDF like a normal song in ST3.
The ability to have, or have not, a backing track attached.
In PDF that had a backing track i would like to be able to program a timecode so it automatically page turns for me.
In PDF without a backing track to be able to easily finger swipe or foot control the page turns.
The PDF files to be selectable like songs or lyric Songs in the left hand column but that you can have an option that the PDF file opens in full screen and a swipe up on screen chooses the next page swipe down on screen chooses the previous page, a swipe right opens the ST3 normal interface and shrinks the PDF to the lyrics window, a swipe left on the lyrics window brings up full screen PDF again. A foot pedal stop or an end of song , immediately shinks the PDF again allowing you to make a new song selection, this would give you freedom to choose next song quickly if the PDF is playing a backing track you can quickly shink the screen make a new next song selection and get back to full screen again.If you choose Auto play on backing tracks with PDF in full screen the next songs PDF is automatically presented and obays the timecode page turns if they have been programed, and if not programed, a finger screen swipes and foot pedal page turns to be possible instead.
The idea is to use the maximum screen for PDF files so the notation is easier to see at a distence but the flexibility to easily use the ST3 interface to choose next song or manually tweak the ipad controls with a simple swipe in the correct direction to achieve the main tasks which are turning pages, selecting next songs, or perhaps tweaking the backing track on the run.
If PDF file is playing in full screen and my next song is a normal Backing track with auto text and chord i expect to automatically revert to standard screen for that song and if my next song was a PDF song the screen to automatically go to full screen again.
So depending on what file is beeing used i automatically get the best layout for the file used.

I will be adding more ideas in this thread as i think of them and would appreciate anyone to suggest any of their own that might be better or different so we can make the PDF addition the best we can the first time, so Peter doasnt waste his time, i think if this is done well a lot of people will be changing their software prefferences to ST3, but it has to be simple to use, easily setup, reliable and a benefit in some way to the majority of Users.

At first i was sceptical, but after a bit of thought from a different perspective i am hoping to make PDFs do something for me, as long as it is created logically and not just a quick tack on.
I am sure Peter has got it by the horns already, ST3 has certainly grown in to a very powerful tool lets keep it growing in the right direction and that is to make Stage performers life easier so they can concentrate mainly on the audience.