Docs to Go has a feature that will remember the last location that you left off on and open the app to that location. This is a separate feature from the multitasking menu for iOS. Sometimes if the app crashes, you may get stuck in a state that you can’t get out of.
You can fix this by following this chain.
iPhone Home screen > settings app > DTG > turn off remember app state
Make sure you exit out of the app after doing this.
You can exit an app by double pressing your home button and swiping up on the DTG app.