In the examples that follow, I use Apple’s TextEdit as the prototypical application. Other applications may need to be updated to take advantage of all the new features described here.
Documents in the Cloud
Probably the biggest change to opening and saving documents in Mountain Lion is the addition of “Documents in the Cloud.” For the first time, Open dialogs offer two main choices for where to save and locate files: “iCloud” and “On My Mac” (in some sense, that should be “On Your Mac;” you won’t be opening files on my Mac).
A TextEdit Open dialog in Mountain Lion, showing the new iCloud option
The On My Mac option works the same way opening has done in prior versions of OS X. Essentially, you navigate via the dialog to the Finder location where you want to be. With the iCloud option selected, you access documents previously stored in the cloud. To get documents to iCloud in the first place, you can save them via the iCloud item in Save dialogs.
The main advantage of using iCloud here is that you can access the same document from any Mac running Mountain Lion that is logged into the same iCloud account. If there is a matching iOS app for your Mac app (there is not one for TextEdit), you will similarly be able to access iCloud-stored documents from your iOS devices. Any change you make to a document on one device will be immediately reflected on all your other synced devices.
From the iCloud display of your files in Open dialogs, you can organize iCloud-stored files into folders. To create a folder, just drag one document on top of another. You can also delete files from here.
One type of Save dialog in Mountain Lion
To make sure you’re set to use Documents in the iCloud, first go to the iCloud System Preferences pane. From here, sign up for (if you haven’t done so already) and log in to your iCloud account. Next, enable the Documents and Data selection. [Note: If you later disable Documents and Data, all your iCloud-stored documents will be removed from your Mac. However, they remain in iCloud and will return if and when you later re-enable the option.]