Updated November 20th, 2015.
You can password-protect a Pages document on your iPhone or iPad. No one can open it without the password. This way, if your iPhone or iPhone is unlocked, your document is still protected. It’s really easy to do.With a Pages document up on your iPhone or iPad, look for the wrench at top right and tap it.
Tap where it says “Set Password”
Give your document a password, enter it a second time, and enter a hint. There’s no back-door into a password-protected Pages document so the hint is essential should you forget the password.
Pages documents show locked icons when they are password-protected. See below.
When you try to open a password-protected Pages document on your iPhone or iPad you’ll see a message asking you to supply the password. If you can’t remember it, try again. If you still can’t remember it, try one more time– the password hint doesn’t appear until the third failure.
And that’s all there is to it.