Pretty good

Since iOS has no finder, this is great for managing iCloud Drive. There is one problem though, using iCloud files through GoodReader is very slow, even if you download them. Also, if you switch apps, even if only for a slight moment, it takes at least 7 seconds before the app is ready to use again when you switch back because it seems that the app needs to reinitiate. This definitely needs to be resolved, very annoying.

OGMedic about GoodReader PDF Editor & Viewer