What kind of data is hidden in a Microsoft Word document?
Word allows you to leave comments and annotations throughout a document while reviewing it (Go to the Review tab for those features). If you are sharing the document, you'll want to clear those out when the final version is done. Hidden metadata and personal information like the name of the author, company, and who last saved the file is stored, as well as watermarks.
More importantly, a Word Document will track and retain all content that was deleted. If you often reuse documents to retain a similar look and feel, it's pretty likely you are retaining a lot of text that isn't intended to be in the file. That text might not display in your document, but someone with a little know-how could reveal it. Let's look at a real-life situation where this would cause a negative impact:
Let's say you start with the same file for project proposals with your clients, you simply change some of the content around, save the document, and send it off. The content from the original proposal is still in the document. If the original document had sensitive information in it, it could become compromised.
How to remove hidden information in a Word Document
Fortunately, checking for and removing that hidden information is simple. Save your document and click File. Click Check for Issues and select the Inspect Document option.
The Document Inspector will pop up. Be sure all boxes are checked and then click Inspect.
After a moment, the Document Inspector will tell you what types of information is stored in the document. The first two options are the most important for privacy - click Remove All next to Comments, Revisions, Versions, and Annotations and Document Properties and Personal Information. If the Document Inspector detects Invisible Content or Hidden Text, remove those as well and then close the Document Inspector.
Before you save your document, check it. Ensure that nothing was removed or adjusted visibly throughout the text. Once you review the document, save it.
Now you'll have a fresh document that doesn't retain all of the text and information from previous versions.