[WORDPRESS] Restrict certain pages with a login

We have a WP with the purpose of displaying different collections of prints and paintings. On the WP there are 2 pages that should be restricted for logged in users only. Because they don't want anyone copying their work. One page contains the portfolio. It's a 3x3 grid, with each tile in the portfolio representing the categories. If you click on a category you go to a page which contains the prints, it's this step that need a login between. The other one is a page where you can download the catalogues in PDF, this page also needs to be protected with a login. I've already tried a couple of plugins but none does what I really want. The login pop-up should also contain a register button. If they register (more then just username/e-mail, but name, firm, tel, email, password) they should get a mail telling them their registration is under review. The website owner need to approve of the registration. If approved the vistor receives another notifcation. The main issue is that the theme (with the muffin builder included) seems to overrule the plugins I tried to use to restrict those pages. I'm working with a 4.1.7 WP with BE theme on it.