Zotero is a free and open-source reference management software to manage bibliographic data and related research materials, such as PDF files.
How to Videos on using Zotero
Zotero How To - https://www.zotero.org/support/quick_start_guide
Getting Started with Zotero - https://youtu.be/QJ6Vgy0VCOg
Zotero Quick Start - https://youtu.be/_OvKsCrW4hM
Zotero in 30 Minutes - https://youtu.be/sCFME6yxVvM