The Rights Management Add-on for Internet Explorer is a way that Windows users can view files with restricted permission. These restrictions help people to prevent sensitive documents, Web-based information, and e-mail messages from being forwarded, edited, or copied by unauthorized individuals.
Document authors, Web site authors, and creators of Web-based applications can deliver protected information by restricting permission. This provides protection, not only while the information is in transit, but also after the recipient of the information has received it.
Authors can set restricted permission to limit what a reader can do with the content they receive. These restrictions are customizable, that is, one person may view the document but not print it, another may do both, and a third person may view and print the document, but only for five days.
Authors can restrict permission to Web-based information as they create it, and then save the content as a rights-managed HTML file (with the file name extension .rmh). If the readers have installed the Rights Management Add-on, they can open the file and use the contents, based on the permission that the author has given them.
News source: Microsoft Download Center