Popup shown before accessing PDF found by Google

I've been tasked with having implementing a google custom search engine with PDF searching capabilities. While this alone would be easy, one of my requirements involves having a popup appear before access is granted to the pdf. The intention is for users of the website to enter information about them so that the website owners can get an idea of what kinds of people are accessing their website.

Is it possible for a user to click on a link in google search, have a credentials popup appear and only after entering the information correctly be directed to the pdf? If so, what would be the best way of going about it? I am currently working with HTML5 and Javascript.