Nature of hidden information
Office documents may invariably contain hidden data and personal information such as comments, track changes, revision work and ink interpolations particularly in edited documents. Quite often these types of hidden information may be sensitive in nature or information meant to be hidden from the recipient. These types of information, if not securely hidden, can enable others to know names of people who worked on the document, comments from reviewers, and the original content of documents and the subsequent alterations made to them.
Document properties, more widely known as metadata, include critical details about a document which need to be safely hidden. There are also other types of details that are automatically maintained by Office programs which have to be made inaccessible to others. If any specific features had been used, then the document might also contain personally identifiable information such as the name of a person, mailing address, e-mail Id, IP address, or personal information about people associated with another program.
The hidden text may also include e-mail headers, review particulars, slips exchanged and file path information for publishing Web pages. As is well-known, Word documents and Excel workbooks can also contain information in headers and footers. There can be a watermark on Word document.