Trim Versions and Saves
Here are two final tweaks to trim file size when you find functionality dragging. If you’re using the versioning feature, delete as many of your saved versions as you can. All of these old versions are tucked right into the file with your current one, to be dragged along every time you open it. In fact, unless company or departmental policy forces you to use the versioning feature, don’t do it!
Finally, you might try turning off fast saves by choosing Tools > Options, clicking the Save tab, and clearing the Allow Fast Saves check box. The fast saves feature saves changes each time, rather than saving the document itself. While this is faster each time you click Save, Word keeps track of all the changes for each save and drags them around until it finally reconciles them with a traditional save.