Is there a way to allow users to edit their email address in a Preference Center page?

There is no way to have a user edit their email address within a Preference Center page; a Preference Center just populates known subscriber data on a page.

However, you can use a Landing Page to allow users to add a new email address.

If you want to populate a user's email address on the Email Preference Center page, you can display the current user's email address on the preference center using the [EMAIL] merge tag.