Zotero

PDF documents are automatically retrieved when you use the Zotero Connector, this is the best way to add items to your library. However, if you have PDF files already saved on your computer and you want to add them to your library, Zotero Desktop can create a bibliographic record from the PDF.

Simply drag the PDF file into Zotero library central pane, this is also the easiest way to attach a PDF file of an article to its corresponding entry in your library:

• Drop a file in between library items or in a collection and Zotero will copy it into your library as a standalone item. 
• Drop the file onto an existing item and Zotero will attach it to that item. 

Alternatively you can attach files to an existing item in this way:

• Click on the Add Attachment icon at the top of the central pane.
• Then select Attach File.

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If you have PDF files stored on your computer, you can drag the files into your Zotero library. If the PDF has a DOI, Zotero will automatically find the 'metadata' or bibliographic information and populate the relevant fields.