Adds a recipient who opens the document with owner access: every permission, including changing the encryption.
public PdfPublicKeyEncryptionOptions AddOwner(X509Certificate2 certificate)
The recipient's X.509 certificate with an RSA public key; it must not be disposed before the save.
ISO 32000-2 §7.6.5.2, Table 24, bit 2: permits change of encryption and enables all other permissions.