Don't be at Word's mercy where hyphenation is concerned. Force the issue by inserting an optional hyphen.
Word doesn't hyphenate content unless you tell it to: From the Tools menu, choose Language, select Hyphenation, check the Automatically Hyphenate Document option, and click OK. Furthermore, setting the Hyphenation Zone option lets you control, a bit, where Word hyphenates a word. The default setting of 25% is adequate for most uses. But even at its best, Word won't always insert the hyphen where you want -- you are somewhat at Word's mercy. When this happens, insert an optional hyphen by holding down the [Ctrl] key as you press the hyphen character key (-). If the word falls at the end of the line, Word will use the optional hyphen. If the word doesn't fall at the end of the line, Word won't display the hyphen character at all. To display optional hyphens on screen, choose Options from the Tools menu and then click the View tab. Select the Optional Hyphens check box in the Formatting Marks section and click OK. In Word 2007, click the Office button and then click the Word Options button. Click Display in the left pane, select the Optional Hyphens check box, and click OK.