"GroupDocs.Annotation for .NET library is a web-based framework which provides features for annotating different types of documents in a web-browser without having to install plugins or middleware on the client. With GroupDocs.Annotation, end users can view and annotate PDF, Microsoft Word, Excel, Outlook, PowerPoint, OpenOffice, AutoCAD and other types of documents and image files. The library comes with a set of commenting and markup tools, including: rectangles, polylines, watermarks, point and area notes, text markup and strikeouts. In this article I'd like to help you discover the GroupDocs.Annotation for .NET library's basic functionality: how it works, where annotations are stored, how to manage users, etc. I'm also going to show you how to use the library in an ASP.NET MVC application. The sample project described in the article is based on MVC5, but most of the code can be used with any other versions of the MVC framework."