Restrict certain pages for employees only?

I have been looking and can’t find a plugin or method to do this, hopefully someone can help this WP newbie.

On my site https://www.mysite.com I have pages that I want open to everyone which contain company information and such. Other pages will have downloads and proprietary information that I want only available to my sales reps.

How can I do this without opening registration/subscription to the general public?