Zotero
Zotero is a free tool that allows you to add content in your web browser to your personal library. Zotero is available as a plugin for the Firefox, Chrome, or Safari web browsers, or as a standalone version. With Zotero you can add PDFs, images, audio, video, and more from the web to your personal library. Zotero can also help you cite your sources and share your sources with others.
Zotero help links: