You can set a pass word fora document normally. It can be cracked if you really need to, but it would provide a basic level of security.
Also hiding the data deep within a normal file helps to obfuscate the info. I.e. 3 or 4 pages into an existing file so that it's not just a blank pages with 4 lines of user/password info.
How secure do you need it to be ? Best in mind the wife will need to be able to access it .... And knowing mine, she would forget how to if it was a complex process to access.