Estoy descargando archivos del servidor usando la clase DownloadManager

Esto es lo que estoy haciendo

public void downloadPdf(String url, String sem, String title, String branch) {
    Uri Download_Uri = Uri.parse(url);
    DownloadManager.Request request = new DownloadManager.Request(Download_Uri);

    //Restrict the types of networks over which this download may proceed.
    request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI | DownloadManager.Request.NETWORK_MOBILE);
    //Set whether this download may proceed over a roaming connection.
    request.setAllowedOverRoaming(false);
    //Set the title of this download, to be displayed in notifications (if enabled).
    request.setTitle("Downloading");
    //Set a description of this download, to be displayed in notifications (if enabled)
    request.setDescription("Downloading File");
    //Set the local destination for the downloaded file to a path within the application's external files directory
    request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, title + "_" + branch + "_" + sem + "Year" + System.currentTimeMillis() + ".pdf");

    //Enqueue a new download and same the referenceId
    downloadReference = downloadManager.enqueue(request);
}

cuando la descarga se completa, si el usuario hace clic en la notificación, debe abrir ese archivo, ¿qué debo hacer en este código?

 BroadcastReceiver onNotificationClick = new BroadcastReceiver() {
    public void onReceive(Context ctxt, Intent intent) {

    }
};

Por favor ayuda