Papers2 is a competitor with reference managers Endnote, Zotero, Mendeley, and RefWorks and has features of all of those for managing a library of citations, pdfs, searching for and sharing scholarly articles, and adding citations to manuscripts. For a review see PLoS Blogs: Papers2: The Reference Manager Made with Love
Also, Introduction to Papers2
A license for Papers2 for Mac or Windows can be purchased and downloaded from the web site or Papers2 for iOS can be purchased from iTunes.
You may find that you can only access databases like Web of Science or Scopus through Papers when you are on campus and using campus IP ranges. PubMed, as a free database, can be used anywhere.
If you need the MSU proxy server string, it is: http://ezproxy.msu.edu/login?url=
Access has been enabled for MSU's Web of Science subscription to work with Papers2.
(A glitch caused problems with Web of Science access through Papers, but Papers 2.5.5 update for Mac restored the functionality. This may not yet be restored for Windows.)
Documentation for how to use and access this service is available at: http://wokinfo.com//media/pdf/wsdownload/
User Name: wsl
Access has been enabled for MSU's Scopus subscription to work with Papers2.
MSU Scopus Account ID: