Ask HN: What do you use for a company wide documentation tool?

I currently work at a company where I've built a marketing automation tool focused on local businesses. I'm trying to make sure all staff are trained on how to use it so that support can be provided to our clients and sales have an understanding of what they are selling.

Right now we are trying to use the new Google Sites (and Google Docs) for internal documentation. The documentation contains guides for setting up and managing accounts within the application and is all internally focused.

Use do use Zendesk Guide (Their knowledge base solution) for our client guides along with some videos clients can watch to learn how to use the app.

Confluence is a possible solution that I've looked into, however, most staff bailed using Jira and are using Asana to manage tasks because Jira was too confusing for them. So Confluence would be too difficult for them to use.

What I'm curious about is what everyone is using for a company-wide internal "wiki" that most staff find "easy" to use and maintain.

On a side note, any suggestions on getting people to adopt a solution would be helpful as well.