If you get the Aura HD, the PDF will be in greyscale, so if you colour documents it will not look well.
To zoom in on a part of the document double tap in the area.
To zoom out double tap again.
You have to options to
- zoom in/out
- fit to width
- fit to height
- rotate the document
To move to a different area you can hold and drag.
This video will explain the Aura HD PDF features better:
https://www.youtube.com/watch?v=LK-1VY9x4DE