I'm never keen on directly opening Word docs within browsers - I like to be able to zoom in and change the view etc - One possibility is to have them inside a password protected zipped folder for download and unzipping to PC by the viewer - placing the download links within perhaps an already protected area within the site - if you already have one
Or if you really want to dsiplay them in a browser just have that area protected separately I expect it is straight forward opening from a link.