the backup of a document is very important, especially if it is a valuable thing for us, if some people are backing up the document in the notes or facebook inbox or in our email, that's a little thing we can do for the security of our account, including I also reserve this is for my own security
What if your Facebook account attack by hack or your email? What will may happen?
Well for me it's better to write it in paper and put it on the safe place.