If you've switched from Windows, the way OS X handles the saving and storage of documents can be confusing at first. In recent iterations, OS X has introduced tools for easy duplication and version control. It has new means of storing documents--through iCloud--and has changed options you're used to seeing, such as Save as.
In this tutorial, I'll show you the uniquely different document model, in OS X, and how to use some of the options that you may not already be familiar with.
With the launch of iCloud, and its subsequent integration into the operating system, cloud storage has become a much more integral part of the document model in OS X. Now your documents aren't always stored locally. This allows you to access documents across multiple Macs and iOS devices without needing to plug in the traditional USB drive to physically move your content.
If you haven't done so already, it's best to sign up for an iCloud account and then log in to the iCloud preference pane in System Preferences.
Documents in the Cloud
One of iCloud's core features is Documents in the Cloud, a service that stores files—and some other application data—in the cloud for access across multiple devices. In Mountain Lion, this service was fully integrated into some Apple's own stock apps alongside traditional, local storage to an extent where you might not even notice the difference. In fact, if you open up an app like TextEdit or Pages, you'll first encounter a document browser like the one below, listing your iCloud-stored documents first by default.
Any documents you open from here are saved and stored in iCloud, meaning any changes you make are stored in the cloud and automatically updated in any other copies of the app you might have on other machines.
In some cases, such as the iWork suite, you'll also be able to open and edit these documents further on your iOS device (with any changes made there again being sent to the cloud and updated on your Mac). If, however, you want to create or load a document locally, switching to the On My Mac tab in the top-left corner will allow you to browser files stored on your Mac or any connected storage volumes.
Initially, your local files and those stored in the cloud are kept separate but, if you search for a file using the top-right search bar, you can switch to the All tab to view results across both your local and online storage.
Though many Apple-developed and third-party apps now use this form of Documents in the Cloud integration, you may still encounter some apps that only use local storage. In these cases, you'll typically save your files to the Documents folder or a sub-folder therein.
Saving and Storing Without iCloud
iCloud might not always be around or, for one reason or another, you might prefer to save locally. Though iCloud storage has become a staple storage option alongside the local alternative, keeping your files on your Mac is still a viable option when you need it.
At any time, you can change the name of a document or the location where it's stored by clicking the downwards arrow in the title bar of your app and modifying the options there.
If this menu shows iCloud in the Where field, your document is being stored in the cloud. You can switch this to any local volume and your document will be brought out of the cloud and back into the local world of on-Mac storage.
The familiar Save as option—to save a document as a new, unique version—is hidden in OS X and, in the case of most apps, is only revealed when you type save as into the search field under Help in the menu bar. Doing so will allow you to select a new name, new tags and choose a new storage location, online or off, irrespective of where the original file was stored. You can then hit the Save button to create your new copy.
Alternatively, you can just duplicate the document by opening a new, unique copy simultaneously by selecting File > Duplicate. Instead of simply saving the document again as a new copy, while keeping the last-saved version in its original place, the Duplicate option keeps both versions open so that you can work on separate forks of the same piece. The first time you manually save the duplicate copy (through Command-S or File > Save), you'll be able to choose what to name it and where to store it.
After initially saving, you'll find that OS X will automatically save your changes, allowing you to quit out of a document without the traditional confirmation. You can, of course, manually save changes at any time by using the Cmd-S keyboard shortcut or clicking through File > Save.
One feature that newcomers to OS X may not be entirely familiar with is the system for managing versions. This utility, integrated by default in many apps including Apple's own, allows you to easily locate older versions of your documents and revert to them. And OS X does this all in the background as it saves.
To locate and revert to an older version, you can often find the option to do so in File > Revert To > Browser All Versions... though if that's not available, searching for versions in the search bar under Help may return a result.
You'll then launch into a Time Machine-esque view, presenting your current document side-by-side with the available older versions. Scrolling through the tabs on the right will allow you to browse and select a different version to compare. Clicking on either the current document or the backup version will allow you to zoom in and scroll through the document so you view it in its entirety.
Then, click the Restore button to revert to the selected backup or click Done to return to the existing iteration. It's as simple as that.
When you get used to how OS X deals with documents and files, you're able to reap the benefits of an operating system that can store and share your documents across all your devices, keeping them in sync and autosaving so you don't even lose that important edit.
If you've switched from Windows, or just still haven't got to grips with the document model in OS X, be sure to let me know in the comments and I can help you out.