As far as I know, manipulations with Word documents are included as a part of OpenOffice UNO (Universal Network Object), Java binding is available. (After all, the OpenOffice application can work with all version of Microsoft Word documents, and the product is Open Source.)
See:
http://en.wikipedia.org/wiki/OpenOffice.org[^],
http://wiki.services.openoffice.org/wiki/Documentation/DevGuide/OpenOffice.org_Developers_Guide[^].
There is a number of commercial products, you can Google to find them.
—SA