Gets or sets how the saved file is encrypted for certificate recipients with the public-key security handler;
null (the default) keeps the document's own encryption.
public PdfPublicKeyEncryptionOptions? PublicKeyEncryption { get; set; }
ISO 32000-2 §7.6.5. Like Encryption, the saved file has a new encryption dictionary and file encryption key, whatever encryption the document was read with, and its output is not deterministic (random seed, CMS keys and IVs). Cannot be combined with Encryption or RemoveEncryption, and an incremental update (IncrementalUpdate) refuses it. A save without any recipient is refused.