Hi,
Forget it, there is no Feedback, and the plugin slowly stops working. Last week I bought the Pro Version to test it out, and quickly I noticed, that search results are not linked to the documents...
Don't try "Document Reviews": no support since last year July. The plugin encrypts the documents and lost the connections to the documents within the last 2 months.
At the moment I'm testing Media Library Assistant for a bit of document management: Incredibly great support, good funcionalities, great documentation, but no access restrictions (as far I've seen):
https://wordpress.org/plugins/media-library-assistant/
Good luck