Set Up WebDAV in Pages on iPad

I want to be able to download and upload files to and from my Amazon S3 cloud storage directly within Pages and Numbers on my i[Pad. I had this working for a long time, but unfortunately I had to reinstall the iOS6 versions of Pages and Numbers because the iOS 7 version (Pages 2) creates files that are not openable on my older Mac. Both Apps work fine again, even in iOSt, but now I want this cloud facility to work again. I realise that I can get the files to and from Amazon using iSME, but that is another step or two that I would rather avoid.

However, when I get to the +/Create Document/Copy from WebDAV setup window entitled "WebDAV Sign In" , enter details of my amazon server, username and password I get a message "An error occurred. Please try again".

Does anyone have any advice on how to link Pages to Amazon S3 using WebDAV? I suspect that the formatting of the server and username details is the problem. Unfortunately, I cannot find my notes from when I originally set it up successfully.