To upgrade the app, please follow the steps below:
1. Sign out from your Apple ID account in iOS Settings > iTunes & App Store > tap your account > Sign Out.
2. Reboot your device by simultaneously pressing and holding Home and Sleep buttons for 10 seconds.
3. Sign in to your Apple ID by opening App Store > Apple ID > Sign In.
4. Make sure there is enough free space on the device to fit the new apps.
5. Open Updates > Purchased > Printer Pro > tap the Update icon