System for displaying and managing files towards customers on website

For numerous years we have used a wordpress site with a WP post based system for displaying .docx, .pdf, .pptx etc. reports towards our customers on our website.

Today we use the following procedure when uploading a report:

  1. Creation of post in WP.
  2. Populating title, description, featured image.
  3. Upload of report into WP-media.
  4. Using shortcode for paywall -> clickable link for download of report

We are now moving towards a customer portal not based on WP but rather html5/bootstrap frontend and PHP/MySQL backend to improve tagging and user customization. Is there a open source or paid alternative that is in the regions of a CMS and a document management system?

So in other words, is there a system/framework, partial or in its entirety that could assist in this process, outside of the WP environment?