ReadCube is an application that manages .pdf documents. It scans .pdf libraries, identifies metadata, makes the library searchable, allows the creation of notes on specific .pdfs, and aids in citing pdfs. It can be used in conjunction with citation management software such as EndNote or Zotero to create bibliographies for papers.
Readcube can be downloaded to your desktop from https://www.readcube.com/. If you choose to subscribe to ReadCube Pro, you can also download apps from the Apple and Google app stores that will sync with a cloud based library and your desktop.