With the recently released 2013 versions of iWork for OS X and iOS, syncing documents across Macs, iOS devices and even iWork for iCloud is now a seamless transparent process: Open and edit a document in one location, and the changes are instantly reflected at every other location that has access to the file. With very few exceptions, a document's appearance remains identical on each platform. Warnings about file conversions and omitted features have all but vanished.
For anyone who has struggled with iWork file syncing over the years, this is fantastic news. It wasn't always this way.
In the beginning...
When Apple introduced iWork for iOS apps in 2010, transferring an iWork '09 document between a Mac and an iPad required a tortuous procedure mediated by iTunes. To transfer a file, you manually exported or imported it; there was no live syncing. Transfers also required converting the document to the matching platform-specific format. Especially when going from Macs to iOS devices, this often meant stripping out features unsupported by the more limited iOS apps.
In 2011, with the introduction of iCloud, true syncing of iWork documents arrived--but only among iOS devices. Transferring a document from a Mac to an iOS device required an intermediate stop at iCloud. From there, an iOS device could access the file (assuming you had iCloud enabled on the device), converting it to the more feature-limited iOS format. Any editing done to a file on one platform had no effect on a copy of that file previously transferred to the other platform.
The release of Mountain Lion in 2012 was a giant step forward. At last, you could "live sync" iWork documents among Macs and iOS devices. After editing a synced Pages document on an iPad, for example, the changes would automatically appear on a Mac, even if the document was open in Pages on the Mac at the time.
The primary remaining downside was the differing multiple iWork file formats. Moving across platforms required document file conversions that often resulted in document feature loss or related incompatibilities.
Three different file formats came into play.
First, if you locally saved a iWork '09 document to your Mac (I'll use Pages as the example app), it saved in the "original" Mac iWork format--with a .pages extension at the end of the file's name. While the Finder did not treat this file as a package (that is, no Show Package Contents command showed up in the document's contextual menu), it was indeed a package. To pry it open, you could use a utility such as Pacifist. Inside, you'd find several items, most notably an index.xml file which contained the primary content you created.
If instead you saved a Pages file to iCloud, it adopted a different format. To distinguish it from the original format, a -tef suffix was added to the end of its name. OS X recognized this format as a package, openable via the Show Package Contents command. Inside, you'd find that the index.xml file was gone, replaced by a file called index.pages (depending upon your settings, the .pages extension might not appear in Finder windows). This .pages item was itself a package: it contained an index.xml.gz file. If you double-clicked the .gz file, a decompressed index.xml file appeared; this was essentially the same as the index.xml file from the original format.
At this point, you may be wondering how one can examine files stored on Apple's iCloud servers. You can't; not directly. However, local copies of these files are maintained on your Mac. For Pages, for example, you'll find them at ~/Library/Mobile Documents/com~apple~Pages/Documents.
If you created a document in Pages for iOS, or if you used the iOS app to open a Pages document placed in iCloud by the Mac, a third format was required. This format retained the same -tef name as already described. However, inside the package, an index.db (database) file replaced the index.pages item. This was the only format compatible with iOS and the only one incompatible with Macs.
Moving files between Macs and iOS devices still required converting files to the proper format. The good news was that users were typically unaware of all of this complexity. The required conversions were handled automatically behind the scenes. While this situation was less than ideal, it worked well in most cases. You could at least see the light at the end of the tunnel.
One format, multiple platforms
With the release of the 2013 iWork apps, we've emerged from the tunnel altogether. There is now only one file format for all app variations. Whether you save or transfer an iWork document to a Mac, an iOS device or iCloud, the document's format remains identical. As a result, files live sync across platforms without any of the compatibility issues that plagued prior versions.
The names of these new iWork documents will be familiar. For example, the names of Pages documents still use a .pages extension. The -tef variations are gone. Inside a document package, however, the format is different from any of the ones used with the prior iWork apps.
The primary item in the package is an index.zip file. If you unzip its contents (I again used Pacifist to do this), you'll find that the XML content has been replaced by multiple .iwa files. Although Apple hasn't offered an official rationale for this shift, the speculation is that the smaller binary .iwa segments allow for faster loading in iCloud and on iOS devices.
This unification of formats would all be perfect, except for one thing. As I've detailed elsewhere, to achieve this cross-platform compatibility, Apple dropped numerous '09 features from their iWork '13 apps. Apple has promised to return some of these missing features over the next few months. In the meantime, if these losses leave you dissatisfied, you may want to keep using the older iWork '09 apps.
But what if you've already created or converted documents using the new versions? If you open an iWork '09 document in an iWork '13 app, the document automatically converts to the new format. However, this is strictly a one-way process: iWork '09 apps cannot convert or otherwise open iWork '13 documents.
There is, however, a work-around. For example, to manually convert new documents to the Pages '09 format, open the document in Pages '13 and go to File > Export > Pages '09; there are matching options in Numbers and Keynote. Alternatively, you may be able to revert a converted document to its prior '09 format via OS X's Browse All Versions option. And don't worry about finding your old apps after you've updated to iWork '13. The iWork '13 installers save the older versions in your Applications folder.
The same doesn't hold true on iOS. If you've upgraded to the latest versions of iWork apps for iOS, there is no Apple-supported way to revert back to the older versions of those apps. Furthermore, documents saved with the new iOS apps use the new iWork '13 format. So if you keep using the '09 apps on the Mac, you'll probably have to give up syncing the documents with iOS devices. Otherwise, you'll have to manually convert the iOS files back to the iWork '09 format, via the option in the Work '13 app, each time you want to re-open the files in Work '09 on the Mac.
Still not sure what version of the iWork apps you want to use? Apple makes it easy to try out the new '13 upgrades. For anyone who owns the prior iWork versions, or buys any of Apple's latest hardware, the new versions are free.