Zotero recently released it's newest update - Zotero 6. This new edition of Zotero includes a new PDF reader, allows you to extract annotations from your PDF attachments (something you previously needed the Zotfile Add-on to do), and enables you to add your notes to a Word document (for annotated bibliographies). To update your Zotero, simply go to the "Help" menu in Zotero and click "Check for Updates."
What is Zotero? How do I install it? What does Zotero do? How do I collaborate with Zotero? All these questions and more answered on the Quick Start Guide.