EDocman is the leading document and files download manager extension for Joomla. Building based on Joomla Access Control Level System (ACL), Edocman gives you a very powerful, flexible permission system which you can use to control who can access, download, manage your documents from both front-end and back-end of Joomla site. Especially, Documents Indexing tool can be used to scan PDF, MS Office files as soon as they are uploaded.
Demo: https://joomdonation.com/joomla-extensions/edocman-joomla-download-manager.html