Scramble Assistant for Word
http://payneconsulting.com/products/scramword_free/

Scramble Assistant for Word allows you to scramble the characters in a document in a way that the formatting of the document remains intact, but the content of the document is scrambled to make it illegible. They also offer a retail version of this product that provides both redaction and scrambling options. The redaction tool is excellent for hiding selected text within a document. This has been added to Privacy Resources Subject Tracer™ Information Blog.