Trying to find docs or a module where certain logged in users/groups can access certain parts of the site.

Basically we want to have a portal for referral partners to login and can see certain documents, pricing, contracts, etc. I looked for a module I see one for version 8 and had one review only. 

Is this something built in and im not using the correct search term to find it or is this something that has to be custom done?

I know the customers have a portal where they can view invoices, quotes and all that. I would like the same concept but for another group, could actually make it part of the user portal as well I guess.

Thanks