iPad Pages Password Protection
You can access the protected files by entering the password.  However, you will get the warning that by opening the document it will become a Pages for iOS document, and thus will no longer be password protected.  You do have the option of 'Opening a Copy' thereby preserving the originals password.

This could be useful if you just need access to the document to read it and then deleting the copy.  Not so useful if you need to edit the doc and save it and have the password intact.