What you're looking for is called a "knowledge base" or "help desk", and there's a new SaaS for it almost every month. Here are a few for starters:

http://helpjuice.com/

http://www.desk.com/features/content-management

http://www.zendesk.com/product/key-features

https://www.zoho.com/support/knowledge-base.html

Most of the time it's integrated with a ticketing system, but there's no reason you have to use that part.