Accessing secure files server and updating list of PDF's

Hi all,
I am currently working on a new project that involves an interactive 3D representation of a building and a series of PDF's to accompany it. The project is to be built for IOS.

I am happy with the 3d aspects and showing PDF's locally within the application but I am struggling with some other areas.

The client would like to be able to access PDF's from a password protected server online (Up to me to choose which). When the server has new PDF's added; they would like this to happen in the app as well. So I guess it is a live document list.

I just wondered if anyone had done anything similar or could point me in the direction of some learning resources that could be helpful.

I have looked into using the WWW class and json related assets but I think I need a shove in the right direction. I am new to file management and accessing servers so if this is too much of a pain to do in Unity then the application will have to be split into two parts!

Thanks for any help!