Hi,
You can add a word document (like other files )as an attachment to your KB articles however you can't directly upload a word document as a KB articles.
You will have to transform it to be xml and respect the necessary format.
Note that recent MS Word application allow you to save your word document into xml. You will then need to apply some transformation (using XSLT)to be compliant but can save a lot of time.
my 2 cents
/J