This looks really cool, but apparently it relies on a web service to extract pdf metadata:

>* The Retrieve Metadata feature uses a Zotero web service to find item metadata. The Zotero client sends the first few pages of text from the PDF to the web service, which uses a variety of extraction algorithms and known metadata from Crossref, paired with DOI and ISBN lookups, to build a parent item for the PDF. The Zotero lookup service doesn’t require a Zotero account and doesn’t log any data about the content or results of searches.*

Does anyone know of open source alternatives which are offline friendly? I’ve tried tesseract and was impressed but the layout analysis and OCR made enough mistakes that tasks like bibliography parsing became considerably more difficult.