When automation and word comes to mind, you usually think of COM, Interop and lack
of speed with 40 copies of Word running in the background that you’ve got no idea
how they got there.

Imagine having your own copy of ’Word’ Server Side – callable through APIs you could
easily create and manipulate Word Documents (Docx) and do a whole bunch of things
through the OpenXML.

These Services are to live within SharePoint 2010 and imagine being able to create
PDFs on the fly. 🙂

http://blogs.msdn.com/microsoft_office_word/archive/2009/10/26/introducing-word-automation-services.aspx