Microsoft's latest move is a smackdown on Google AND Apple

Dear iPad and iPhone users: if you like Microsoft Office instead of Apple's iWork suite, but you want to back up your files to Apple's iCloud, Microsoft just made that possible for you.

In addition to letting you use iCloud or Dropbox (via a partnership announced in November) or Microsoft's own cloud storage, OneDrive, to store and share files, Microsoft has opened up its platform to any cloud storage provider.

Office users simply choose 'iCloud" from the Locations picker menu within Office, Microsoft's Kirk Koenigsbauer announced in a post on the Office Blog.

And eventually, they'll use the "Locations" picker to be able to choose other clouds, as well.

Given that there are billions of Microsoft Office files out there, stashed all over the countless number of cloud storage providers, we're guessing that a lot of these providers are going to take Microsoft up on the offer.

But wait, there's more.

Microsoft also announced a plan that will let any cloud software company add Microsoft's freebie online version of Office, known as Office Online, to their websites. That means that any online app that would like to work with Microsoft Office can be set up so that you can open and do light editing of these files, via a browser, without leaving their cloud storage app.

Box, Citrix, and Salesforce are already working on this as a part of Microsoft's new Cloud Storage Partner Program.

This is the first fruit of a bury-the-hatchet partnership between Salesforce and Microsoft signed last May, a few months after Satay Nadella took over as CEO. Before that partnership, these two were huge rivals.

While this new cloud-picking feature seems like small potatoes, it's interesting for a number of reasons.

First, it's a smack-down on Google. As we reported, Google has a plan to grab 80% of Microsoft's Office users. One part of that plan is to treat Office documents like "first-class citizens," Amit Singh, president of Google for Work told us.

But Google's plan does not mean that when you open an Office document from Google Drive, it opens in Microsoft Office. The file opens in Google Appd, but with formatting more-or-less intact via an Office-compatible editor, QuickOffice, that Google bought a few years ago.

If Google wanted to let Drive users open apps in Office Online, it could. We won't hold our breath for that, though. Google is pretty proud of the collaboration features in Apps, and wants to encourage people to use its own software, not give them an escape route back to Microsoft.

This move by Microsoft is also a smack-down on Apple.

On Friday, Apple fired a shot at Microsoft Office. For the first time, it is allowing people who do not own Apple devices to sign up for an Apple ID and use that ID to access a freebie cloud version of its Microsoft Office alternative, iWork. Anyone, on any device, can use now use iWork via web browser.

And a third reason this is interesting is because, oddly enough, Windows users don't yet have the option to choose iCloud or other cloud providers. Microsoft says it is currently working on adding these cloud options to Android, just like, earlier this month, Android users got the choice to use Dropbox.

That means, for the first time in its history, Microsoft is now piling on features for non-Windows users, months to years before they are available to Windows users. For instance, Microsoft still doesn't have a touch-friendly version of Office for Windows, although the touch-friendly Office for iPad is now about a year old. (The full-featured, touch-friendly Microsoft Office is coming with Windows 10, Microsoft's next version of Windows, expected to be out late this year.)

Microsoft used to treat Apple's platforms as second-class citizens, releasing features first for Windows, with Mac users waiting months to years to get the same.

Now, the reverse is true, at least when it comes to the iPad.

And that's so smart. Because, if businesses don't rush to Windows 10 tablets and instead stick with Windows 7 for years for their PCs (like they did with XP), while buying iPads for their tablet needs, Microsoft still wins - it will still keep them as Office customers.