Some might suggest you download an app to convert a picture to a PDF on the iPhone, but the truth is you can do it for free without any apps.

Amazon's Kindle (or Kindle app) supports not only ebooks, but also PDFs. But reading PDFs on a Kindle requires a little help. Here are several different ways to convert and read PDFs on a Kindle.

When it comes to converting file extensions on your iPhone, don't worry about downloading a third-party app when you can make the changes yourself.