GroupDocs – Document Sharing and Collaboration in the Cloud
http://groupdocs.com/

Upload, Convert, View, Sign and Compare documents with your colleagues or business partners in realtime. Their easy to use collaboration platform has been built to allow you to work with your documents how you want and need them. Simply register and start using it. Sign up is free, so there’s nothing to lose. This has been added to the tools section of Research Resources Subject Tracer™ Information Blog.