I Certainly Wasn't Aware Of This

What Secrets Are Your Computer Documents Revealing?
Are you revealing confidential information when you send someone email? If you attach documents in Microsoft Word, Excel or PowerPoint there's an excellent chance you're doing exactly that.
When you create and edit documents in these Microsoft Office programs, information about you and the edits you make is automatically created and hidden within the document file. This information is called "metadata." Similar metadata issues affect most software programs.
British Prime Minister Tony Blair found out the hard way that Microsoft Office documents hold "hidden cargo." Back in 2003, his office published a report on Iraq's security and intelligence organizations that was cited by former U.S. Secretary of State Colin Powell in his address to the United Nations the same month. However, the Microsoft Office documents meant to bolster his case for intervention in Iraq actually contained metadata that contradicted the official British position. Indeed, the metadata made it obvious that much of the material in the report had been plagiarized!
You would hope that Microsoft would have solved the metadata problem in the intervening four years, but unfortunately, not much has changed. While the newest versions of Office have features that allow you to minimize the metadata in documents you create, many features that create metadata are turned on by default.
Most metadata is pretty mundane like your name and initials (or those of the person that created the file), the name of your company, etc. But it also may contain bits and pieces of previous versions of the document, along with text you thought you deleted!
Perhaps the most important precaution to take to avoid revealing embarrassing metadata is to turn off the "Fast Saves" feature in Word, PowerPoint and Excel. Because of the design of this feature, text that you delete from a document may remain hidden in subsequent versions, even after you save the document. To turn off Fast Saves, click on Tools, then Options, then the Save tab, and uncheck "Allow fast saves."
Another important precaution is to make certain that Word's "Track Changes" feature isn't inadvertently saving previous versions of an edited document. To make sure it's not, Click on Tools, then Track Changes, then Highlight Changes. Go through the entire document to make sure that you've accepted or rejected all changes in it. You can also instruct Word to accept all changes.
Click here for more information on how to remove metadata from Microsoft documents.
One way to avoid problems with metadata altogether is to convert Word documents to Adobe PDF files once you've finished editing them. Adobe files contain their own metadata, but only basic information such as the name of the person who created the file, date of creation, and file location.