Here’s a few ways to write secret messages in MS Word.
Write your message, select it, and change the Font Color to white. Your words have disappeared! The problem here is that if another person highlights the document and changes the font to black, your words come back. Let’s try another option.
Select the text and change the font to Wingdings or Webdings fonts. This will ‘scramble’ your text and make it unreadable to prying eyes. But, of course, it’s hardly bulletproof.
Select the text and change it to 1pt. This shrinks the words so that they appear as a thin, slightly jagged line. This might work if you can disguise your text as underlines or line breaks in your document.