private void RadRichTextBox_CommandExecuted(object sender, CommandExecutedEventArgs e)
{
    if (e.Command is PasteCommand)
    {             
        Application.DoEvents();

        bool cursorAtDocEnd = this.radRichTextBox.Document.CaretPosition.IsPositionAtDocumentEnd;
        if (cursorAtDocEnd)
        {
            MoveCaretCommand command = new MoveCaretCommand(this.radRichTextBox.RichTextBoxElement);
            command.Execute(MoveCaretDirections.Down);
        }
    }
}