Prezado Matheus,
Infelizmente não consegui utilizar a biblioteca.
Meu problema é que o arquivo baixa na pasta download, mas não consigo lê-lo.
Rotina de download, funciona e baixa o arquivo na pasta download
DownloadManager downloadManager =
                                (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
  DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));                       long downloadId = downloadManager.enqueue(request);
      DownloadApplication app = (DownloadApplication) getApplication();
                        app.downloadsAtivos.add(downloadId);
 // Classe DownloadReceiver
public class DownloadReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        long downloadId = intent.getExtras().getLong(DownloadManager.EXTRA_DOWNLOAD_ID);
    DownloadApplication app =
            (DownloadApplication) context.getApplicationContext();
    if (app.downloadsAtivos.indexOf(downloadId) != -1) {
        DownloadManager.Query query = new DownloadManager.Query();
        query.setFilterById(downloadId);
        DownloadManager downloadManager =
                (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);
        Cursor cursor = downloadManager.query(query);
        if (cursor.moveToFirst()) {
            String uri =                        cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI ));
           String mime =                       cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_MEDIA_TYPE));
            Uri ArquivoPDF =   Uri.parse(uri) ;
            File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath() +"/"+ "Comunicado-Tecnico-79.pdf");
            File path = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS) +"/"+ "Comunicado-Tecnico-79.pdf");
            File path2 = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
            Intent abreArquivoIntent = new Intent(Intent.ACTION_VIEW);
            abreArquivoIntent.setDataAndType(Uri.fromFile(path), "application/pdf");
            abreArquivoIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            Intent intent2 = Intent.createChooser(abreArquivoIntent, "Abrir arquivo");
            context.startActivity(intent2);
            try {
                if (file.exists()) {
                    Toast.makeText(context,
                            "Arquivo existe", Toast.LENGTH_SHORT).show();
                } else{
                    Toast.makeText(context,
                            "Arquivo não existe", Toast.LENGTH_SHORT).show();
                }
            } catch (ActivityNotFoundException e) {
            }
            PackageManager packageManager = context.getPackageManager();
            if (packageManager.resolveActivity(abreArquivoIntent, 0) != null) {
                PendingIntent acaoPendente =
                        PendingIntent.getActivity(context, 0,
                                abreArquivoIntent, PendingIntent.FLAG_CANCEL_CURRENT);
                Notification notificacao = new NotificationCompat.Builder(context)
                        .setContentTitle("Download terminado")
                        .setContentText(uri)
                        .setSmallIcon(android.R.drawable.ic_menu_slideshow)
                        .setAutoCancel(true)
                        .setContentIntent(acaoPendente)
                        .build();
                NotificationManager notificationManager =
                        (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
                notificationManager.notify(123, notificacao);
                Toast.makeText(context,
                        "Download concluído", Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(context,
                        "Não tem aplicativo para abrir o download", Toast.LENGTH_SHORT).show();
            }
       }
  Toast.makeText(context,
                            "Não tem aplicativo para abrir o download", Toast.LENGTH_SHORT).show();
                }
           }
            cursor.close();
            app.downloadsAtivos.remove(downloadId);
        }
    }
            cursor.close();
  app.downloadsAtivos.remove(downloadId);
        }
    }