I am working on a project in which video streaming is required .In this project i used flowplayer.Is it possible in flow player to hide the video url?
I am also needed to view pdf files in iframe.In it,is it possible to hide url of pdf file?

What is the reason for hiding the URL?

so that another person can not download or view/stream outside the website.

Hiding or obscuring the URL will not prevent that. There are still ways to get to the correct file. Most likely, your webhost provides you with an option to "prevent hotlinking". This will disable access to the file, unless the request is coming from your own domain. Although more difficult, there are ways to circumvent this too.

can you tell me, how to use "prevent hotlinking".

It is usually a setting in your cPanel or WHM. Check the documentation, or ask your webhost.