Best way to document Dwh views

I works in a company that provide Dwh views as an API for external Customers (We use MS-SQL 2008 & 2012).

every once in a while we release new views and updates the existing views.

We have difficult to track and document all the updates and changes (currently it is documented in WORD document).

In addition we got complains from customers telling us that the documentation isn't detailed enough and they want to see Entity Relationship Diagram (ERD), primary and foreign keys - in addition to the descriptions of the views.

My first thought is to make it available online (like other APIs documentation I saw) rather then WORD or PDF document.

My question is, do you have any experience or any suggestion what is the best way to document Dwh views? Do you know any automation tools (free or not) that can help with this task?

Thanks,