Import from websites by using the toolbar add-on: the web importer allows you to import citations, web pages and other documents into your library from search engines and Library databases.
Drag and drop: drag a PDF into Mendeley from your desktop or folders; you can annotate, cite and highlight the PDFs from within Mendeley.
Mendeley detects the document details (author, abstract, keywords, etc.). Documents that Mendeley cannot find details for go into the 'Needs Review' section for manual verification.
Import from existing software: you can import BibTeX, RIS and EndNote XML files so you can transfer your library between EndNote, Papers and Zotero.
Automatically watch folders to add new documents: choose a folder on your computer to 'watch'; when you add papers to that folder, they will automatically be added to your Mendeley library.