If a user password is supplied the viewer application should prompt for a password. If a user password is not supplied no password will be requested to open the document. By correctly supplying either the user password or the owner password, the user will be able to open the document, decrypt it, and display it on the screen. Whether additional operations are allowed on a decrypted document depends on which password (if any) was supplied when the document was opened and on any access restrictions specified using this class's Permissions property.