Pages '09: Locking a Document So It Can’t Be Edited
If you’re using a Mac with OS X v10.7 (Lion) or later, you can lock your document so you can’t edit it by accident, when you only intend to open and view it. You can easily unlock the document at any time to continue editing it.
Open the document you want to lock, and hold your pointer over the name of the document at the top of the Pages application window.
A triangle appears.
Click the triangle and choose Lock.
Hold your pointer over the name of the document at the top of the application window until the triangle appears, click the triangle, and then choose Unlock.