Why can't I install wireless printing on my Mac?

If you're using OS X 10.7 or OS X 10.8, you may see the following warnings when you try to install wireless printing:

• Popup can't be opened because it was not downloaded from the Mac App Store
• Notify can't be opened because it was not downloaded from the Mac App Store

This is because the more recent operating systems have more restrictive default settings in order to improve security. However, you can work around this problem without introducing any security weaknesses by individually exempting the wireless printing software because it is a trusted application:

1. Control-click (or right-click) the downloaded app to run/install it
2. On the popup menu, choose Open
3. On the next dialogue box, choose Open again

You should now be able to install and run wireless printing from your Mac.