Adds a recipient who opens the document with permissions.
public PdfPublicKeyEncryptionOptions AddRecipient(X509Certificate2 certificate, PdfPermissions permissions)
The recipient's X.509 certificate, whose RSA public key the enveloped data's key is encrypted with. Only its public part is used; it must not be disposed before the save.
What the recipient may do; values outside All are ignored.
ISO 32000-2 §7.6.5.2, Table 24: written with bit 10 set (PDF 2.0 writers shall set it) and the bits Table 24 does not use set. A certificate added more than once gets the permissions of the first list that names it (Table 23).