When you create documents in iWork, you can require a password for users to open the file. With iPhone and iPad models that support Face ID, you can use Face ID instead of typing in the password. If you have an iPhone or iPad that supports Touch ID, you can use Touch ID to open your iWork documents.
To unlock password-protected documents with Face ID, first set up Face ID on your iPhone or iPad. The first time you open any locked Pages, Numbers, or Keynote document with Face ID, you're asked to allow the iWork app to use Face ID. This will happen only once per app. You can change this setting in Settings > Face ID & Passcode > Other Apps.
Add a password to a document
With the document open in Pages, Numbers, or Keynote on your iPhone or iPad, tap the More button , then tap Set Password. Enter your password in the Password and Verify fields, then add a Password Hint to help you remember your text password. Make sure that "Open with Face ID" is turned on, then tap Done.
Open password-protected documents with Face ID
When you open a password-protected document for the first time, enter the document's text password. If you've set up Face ID on your iPhone or iPad, you also see the “Open with Face ID” option turned on.
The next time you open this document, you can simply look at your device instead of typing the document's password. If your face isn't recognized after two attempts, you can type the document's password.