If you want to prevent other people from viewing the files in Office2, you can set a four digit passcode that must be entered everytime the app is opened or switched to. To passcode the app, open the Settings page and turn on the Passcode lock switch. You will be asked to enter a four digit number and then to confirm the number, by entering the same number again. Once you have done this, the next time you open Office2, you will be prompted to enter the four-digit number. 
If someone has attempted to open Office2 and entered an incorrect number, you will be shown the number of failed attempts in this screen since the last successful passcode entry.