pdfs: drag to Zotero from the file system, use right-click "retrieve metadata".
docs and pdfs without text-layer or with failed metadata retrieval: manually create items (or use database like google scholar for that purpose), then drag the file to that item.
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docs and pdfs without text-layer or with failed metadata retrieval: manually create items (or use database like google scholar for that purpose), then drag the file to that item.
http://www.zotero.org/support/retrieve_pdf_metadata