 
            | Accusoft.PdfXpressSdk Namespace > Document Class : AddSecurity Method | 
| Exception | Description | 
|---|---|
| System.ArgumentNullException | The Security parameter is null. | 
| PdfXpressException | The Document already has Security. Security has already been removed and it must be saved first. In order to add Security to a Document, an Owner Password must be specified. A Permission specified as being allowed or not isn't applicable for the current EncryptMethod. |