This article shows how to use Text to Speech APIs.

private static TextToSpeech tts = null;
private void startTTS(Context context, final String text){
   tts = new TextToSpeech(context, new TextToSpeech.OnInitListener() {
      @Override
      public void onInit(int status) {
         tts.setLanguage(Locale.getDefault());
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP)
            tts.speak(text, TextToSpeech.QUEUE_FLUSH, null, "Done");
         else
            tts.speak(text, TextToSpeech.QUEUE_FLUSH, null);
      }
   });
}

If you call this method in the OnPDFSelectEnd(String text) of PDFViewAct, you will reproduce the selected text with TTS.

@Override
public void OnPDFSelectEnd(String text) {
   startTTS(this, text);

   /* ..some code.. */
}