I had a friend in med school who wrote a very early note-taking app for the iPad. Turns out that there was no way to render PowerPoint files when the iPad first came out. He realized that the iOS/Mac OS "quick preview" function could be used to take screenshots of each PowerPoint slide. For a brief time, his was the only app that could display PowerPoints (albeit, they were just screenshots!). There's a lot of hidden utility in Apple libraries.