how do I download OS X 10.8 ?

You may buy it from the App store.

Barry

10.8 doesn't seem to be available in App Store. Only 10.8.2 is available.

I'm looking for a previous version of the OS, since the recent update broke scanning on my Canon scanner. Where can I go to download old versions?

Sorry, but you can't. Apple offers only the most recent version. If you didn't already download the earlier version when it was available, 10.8.2 will be the only version you can get. You'll probably have to wait for an update from Canon for the drivers for your scanner if indeed they're not compatible with 10.8.2 and Canon support has no other solution.

Regards.