Zotero: Attach Files

You can attach files to items in your Zotero library by dragging the file over your reference in the Zotero middle column.  Alternatively, you can add attachments using the drop down menu under the paper clip icon above the middle panel. You can attach files by selecting the library item you want to attach to (in the middle column), clicking the paper clip icon and then selecting "Attach Stored Copy of File..."