There are two approaches for presenting a Box file in UIWebView: 1) Use Box View API for presenting the API. 2) Use Box Content API and download a file in Bundle/Document's(local) and the present it in UIWebView.
Here is a tut for using BoxView: http://developers.box.com/viewing-your-first-document/
Login to developer.Box.com first and then u can have access to the link.