If that Mac can open the file, and you've chosen 'Save and Open', it will do so in the appropriate application. If the Mac lacks the necessary application to open the file, but the Mac is aware of which application created it (and that application is available from the Mac App Store), a notification will warn you that you're missing the application, but that you can get it from the Mac App Store. Tell your Mac to get it, and the Mac App Store application will open and direct you to the application. You can then choose to purchase it.
Sign up for CIO Asia eNewsletters.