It's easy to attach files (like PDFs) to items in your Zotero library. There are several ways to add files:

• PDFs are automatically saved as you save citations in many cases.  Zotero checks the UnPaywall service for Open Access articles.
• Have a citation without a PDF? You can try right-clicking the citation and choosing "Find Full Text."  
• Have a PDF in hand?  Drag the file into your Zotero pane.
  • Zotero will attempt to lookup the article information.
  • Dropping a file onto a collection, or in between library items, will copy it into your library as a standalone item. Dropping it onto an existing item will attach it to that item. This is the easiest way to attach a copy of an article to its entry in your library.
• Use the Add File icon in the top menu bar

Supported file types include PDFs, Word documents, image files, and more.

The true power of Zotero is in its note-taking functions. Zotero allows you to go beyond managing citations to developing a fully-searchable database of your research notes.

Notes can be standalone or be attached to a citation.

To add standalone notes, click on the Add Note icon in the Zotero toolbar and choose "Add Standalone Note."

To attach a note to a citation,highlight the item you wish to add a note to and

• either click on the Add Note icon in the Zotero toolbar and choose "Add Item Note" or 
• click on the Notes icon on the right details pane and click the plus sign to add a new note.