Using the Page Resource in Moodle
Summary
...
Step-by-Step Tutorial
...
Now all that students have do do is click on the link to your page and the document opens as a web page in Moodle.
To modify your page just click on the Update tool 
for the page and make your updates. No longer do you need to make changes in Word, delete an old Moodle version, and then upload your new version.