peter i see what you mean, but i gave it some more thought and what Brian said earlier and i do agrre with him that keeping a focus on what Stage Traxx is about, and thats Audio backing and Lyrics and chords, people that reguire sheet music dont normally require backing tracks and there are plenty of page turners out there, once you introduce PDFs people will want multiple files as their music spreads across them then you will have issues of screen size if you zoom out you wont be able to see the detailed notation then you will need to change so many things to suit a minority and unnecessarily complicate ST3 for the wrong reasons, i dont know of anyone in my musicians circle that would benefit from this as they all perform with a backing track and are good enough musos to create music without notation.
ST3 is about backing tracks and some help with lyrics chords and prompts to help on stage live performance, it can now change your midi instruments in sync and lighting, which is great but still more than most people require, if you need a page turner there are plenty of them out there you could even use photo to page turn jpg photo texts.
So my opinion is i say NO to different formats in ST3.
Looping on the other hand is the future that should have been here years ago but no one has done it sucessfully to be used live Ableton live has given it a good shot but its not designed for a large number of musicians that perform live on stage and want simple yet powerful control of their backing track performance.