I have an app that displays multipage PDF files, allowing scrolling through all of the pages, and I would like to add the ability for users to write comments over top of the original PDF by moving their fingers over the screen (this is best on the iPad, with its bigger screen). I'm trying to think of a way to do this. I want to save the edited PDF file as a new PDF file, so that I can reload it in the future and have all of the comments still intact. I would also like the app to work in landscape or portrait mode, so I'd like something that could scale. I'm still in the process of thinking through this problem, and I need an idea for where to start. Does anyone have any experience with something like this? Thanks a lot!