Tim Bray notes that Office 2003 has built-in DRM support. About a year ago I was pretty shocked to discover that Internet Explorer offers that same thing: Rights Managed Add-on for Internet Explorer. This appears to use the same facilities that Tim notes Office 2003 supports:

Using Windows Rights Management Services technology, authors can set restricted permission to limit what a reader can do with the content they receive. These restrictions are customizable, that is, an author can specify that one person may view the document but not print it, another may do both, and that a third person may view and print the document, but only for five days.

Content can be created with restricted permission by using an application that supports Windows Right Management Services, such as Microsoft Office Professional Edition 2003. When an author creates a protected document, Office will also embed a rights-managed HTML version of the content within the file.