Because not everyone immediately updates their software when a new version is released, you may expect to run into problems when sharing 2007 documents with those using Word 2003 or earlier. Luckily, Microsoft anticpated this and included functionality to ensure that 2007 documents play well with others: Compatibility Mode and the Compatibility Checker.

When you open a Word document created in an earlier version in 2007, Word automatically switches to Compatibility Mode in which Word turns off the options that only work with 2007. For instance, you can't apply a 2007 document Theme to a document running in Compatibility Mode.

If you create a document in 2007 from scratch but need to share it with others using earlier versions, you can turn on the Compatibility Checker to find out exactly which features you’ll lose in translation. To run the checker, click the round Microsoft Office button at the very top-left of your Word window. Then, select Prepare | Run Compatibility Checker. You’ll instantly see a summary of items that Word must alter when you save the document to an earlier version.