TOPIC:

How we can add Loading effect while opening PDF file from URL i.e http_link. Currently if you load large size PDF file using HTTP URL then reader take some time to load this file on screen. End user get confused whether file will be open or not? So is any way to add loading effect on screen.

yes, so, you are using PDFHttpStream, you can do like PDFNavAct.java does.
there is OpenTask class in PDFNavAct, to display a waiting dialog while opening need more than 1 second.
to override onPreExecute() method of AsyncTask.