Password-protect a document
You can assign a password to a document so that only those who know the password can open it. Passwords can consist of almost any combination of numerals, capital or lowercase letters, and special keyboard characters.
Add a password to a document
Choose File > Set Password (from the File menu at the top of your computer screen).
Enter the password in the Password field, then enter it again in the Verify field.
Enter a hint to remind you of the password if you forget it.
Select the checkbox if you want to add the password to your keychain.
Click Set Password.
Change or remove a password
Change a password: Choose File > Change Password (from the File menu at the top of your computer screen). Enter the requested information, then click Change Password.
Remove a password: Choose File > Change Password. Type the old password, then click Remove Password.
Password-protected documents stay protected when you share them using iCloud, so your collaborators will need the password to open the document. If the document is already being shared on iCloud, you can add, remove, or change a password in Share Settings.
Note: Documents can have only one password, so if you change the password when you share the document, that becomes the document’s only password.