Mendeley is a free cross-device reference manager and academic social networking tool.
You can easily build a fully searchable library in seconds, cite as you write, and read and annotate your PDFs on any device. Your personalized reference library is securely stored and accessible across your devices. You have the ability to efficiently search and sort your references, documents, and notes all in one centralized place - right down to the keyword you're searching for.
Mendeley can be used online or offline allowing easy access to your PDFs while on the move - highlight, annotate and add sticky notes to capture your thoughts in real-time. It is also fully compatible with Microsoft Word, LibreOffice, and BibTeX. Mendeley permits the sharing of reading lists, references or full-text articles publicly or privately - the choice is yours.