PDF documents are automatically retrieved when you use the Zotero Connector, and this is the best way to add items to your library. However, if you have PDFs saved already which you want to add to your library, Zotero Desktop can create a bibliographic record from the PDF.
There are two ways to add the PDFs to your library:
Bibliographic details may not always import correctly. If this happens, to retrieve the bibliographic information manually, right-click on the PDF file in your library and select Retrieve Metadata for PDF.
If you have PDFs stored on your computer, drag them into the middle pane of your Zotero library. If you have 'Automatically retrieve metadata' checked in Zotero preferences, Zotero will find the bibliographic details and create a record in our library.