You as a marketer would like to know more about the consumption of your product.
A PDF reader app that the client gets for free with the PDF file you send them or they download. They can, of course, open the PDF file in any other app, but you incentive them to use your app by promising them real time up to date data, surprises, etc. The app has two primary functions:
1. Report to you their consumption of the PDF file (how often, how far they read etc.)
2. A real time communication device that adapts to how they interact with the PDF document (where they currently are, what have they already read, etc.)