Android PDF FIle Reader with In-App Purchase

I need a Simple Android PDF Reader with In-App purchase The following are the requirement. 1. The app will have various pds files with thumbnail cover image. 2. There will be a main XML with the details of PDF and link to thumbnail image 3. Users can click on any pdf to download it, and can read it offline. 4. In-App purchase needed before purchasing I want to make the project simple as possible and my budget is limited too.