Checking in using Iphone app and availability of paper boarding passes

I've yet to use the United app as a boarding pass. My father and I will be traveling next week, and I would like to try it out. However, if there are any problems, I will definitely get the I told you so conversation in regards to doing the process with paper boarding passes.

So is it possible to cover both bases, Use the Iphpone app to check in, and then later on obtain paper boarding passes on the internet or at the airport?

Thanks.