Why is my password not working on the Pages app?

You will need the current document password to change or remove the Pages document password. No magic wand otherwise.

Had you chosen to Remember the password in the Keychain option on the original password dialog, Pages would reference the keychain to automatically get the password and open the documents. No mental recall is required, as long as the Pages document remains in the same user account where the password was set.

The surefire means to circumvent memory recall of passwords is to write them down with the filename in a text document. Unless you use the same easily remembered password for all of your Pages documents, human recall is a tricky thing…

Either the keychain or lucid recall will get you past a password-protected Pages document. Nothing else will.

No Apple employees participate in these fellow user-supported, public communities. Unless you contact Apple Support, with Apple-badged employees, and share your current dilemma with them, no one here can resolve your password-protected Pages documents issues, or with Notes on your iPhone 13 Pro.

Check your keyboard input selection again (e.g. A+, U.S., etc) to ensure that it is not entering unexpectedly different characters while typing your password in the Pages unlock dialog. I recommend installing the Apple Support App on your iPhone too.