byte[] SaveDocument(
    DocumentFormat format,
    EncryptionSettings encryptionSettings
)

Function SaveDocument(
    format As DocumentFormat,
    encryptionSettings As EncryptionSettings
) As Byte()

using DevExpress.XtraRichEdit;
using DevExpress.XtraRichEdit.API.Native;
// ...

Document document = richEditControl1.Document;

// Specify encryption settings.
EncryptionSettings encryptionSettings = new EncryptionSettings
  {
      Type = EncryptionType.Strong,
      Password = "password"
  };

// Save the document to a byte array.
byte[] docBytes = document.SaveDocument(DocumentFormat.Docx, encryptionSettings);

Imports DevExpress.XtraRichEdit
Imports DevExpress.XtraRichEdit.API.Native
' ...

Dim document As Document = richEditControl1.Document

' Specify encryption settings.
Dim encryptionSettings As New EncryptionSettings With {
    .Type = EncryptionType.Strong,
    .Password = "password"
}

' Save the document to a byte array.
Dim docBytes() As Byte = document.SaveDocument(DocumentFormat.Docx, encryptionSettings)