Company Intranet using WP?

Currently I have a site used as a back office for a real estate company. It’s using Joomla now but would really love to change it over to WP if it’s possible or even a good idea. Currently the site is used to house documents, many many pdf’s under different groups, forms, marketing etc… The site would need to be membership only and I’ve seen a plugin for Document control wondering what you think? Anyone already doing this? Would love to hear opinions on the idea of doing this, how to secure it to members only approved by me, what best plugin to use for doc management, etc..