Combining smart quotes and inch marks?

You can indeed combine smart quotes and the character that indicates inches, by using the appropriate inch mark character from the system-wide Character Palette. To do this, you will need access the Input Menu at the top right of the menu bar. If you don't have the Input Menu visible, go into the International System Preferences, in the Input Menu tab, check the "Show Input Menu in Menu Bar" option at the bottom of the panel, and check "On" for the Character Palette. This will put a little flag on the right side of your menu bar -- this is the Input Menu.

From the Input Menu, select the Character Palette. With the palette open, choose the Punctuation category. You will be presented with a wide array of punctuation characters, including proper inch and foot marks (which are actually "prime" and "double prime" marks, and are angled, unlike straight quotes). Select in Pages where you want the character to go, and then double-click it, and it will be inserted. The prime and double-prime marks are not considered quotes by the system, and so won't be curlified.