Is there a CRM to host private, customer-specific reports?

I'm tasked with building a customer portal where we can upload documents which our customers ask for, and host them for some compliance period of time. Probably about a year. I've been searching for "private content CMS" but I'm not getting back what I hoped in search results.

I have basically no experience with CMS, but it seems like the "private content" label is not what I'm trying to find. Private content seems to be content which is only published for subscribers, but is generally available to all subscribers.

Is there a term which the CMS industry uses to indicate the problem I'm trying to solve?

If my question isn't sufficient, I'll explain more. We build reports for our clients and they're saved as PDFs. Some of our clients want the PDFs made available on the internet and stored for some period of time which their industry requires. The information in the reports is proprietary, so I need to ensure that customers aren't able to access each others reports.

I'd like to have a portal which I can upload content to, for any of my clients, and then the clients are able to log in to view and download their own reports but not other clients reports.

Hopefully that makes sense.