Zotero is the freely available tool we recommend, developed specifically for academic research, that helps you collect, manage, annotate, and cite your sources.
Zotero's features give you the the ability to attach PDFs, notes, and images to your references, arrange your sources into collections for different projects, and tag them for easy searching. Insert citations to Word or Google Docs as you write and create a formatted bibliography or works cited page with one click.
Check out our Zotero "step by step" guide to try it out yourself.