App store charging twice for same app
I don't know if GoodReader re-issued a new build that was similar in name, but costs more money or if there was a mix up on your account.

Your best bet is to report a problem from within the purchase history using iTunes on a computer since it will have the order numbers (actually they are alphanumeric strings) for both purchases so you can ask Apple's billing support if indeed my guess is the case.

You could also look over the purchase history on iOS - but a developer could remove an old version of an app for sale, and it would no longer appear in the purchased history for download.

Lastly, you could reach out to GoodReader support and ask them if they had a paid upgrade somewhere between the two versions you have in your purchase history. Support for each app is always available from the App Store as well if you want to use that link rather than the one I dug up above.