You can assign a password to a spreadsheet so only those who know the password can open, read, or edit a copy of the spreadsheet. Passwords can consist of almost any combination of numerals, capital or lowercase letters, and special keyboard characters.
To restrict access to your spreadsheet, set a password for it. Passwords can consist of almost any combination of numbers, uppercase or lowercase letters, and special keyboard characters.
Tap 
, tap Set Password, enter the requested information, then tap Done.
When you open a password-protected spreadsheet by entering the password, you can turn on “Remember this password” so you don’t have to type the password each time you open the spreadsheet.
Change a password: Tap , then tap Change Password. Enter the requested information, then tap Done.
Remove a password: Tap , turn off Require Password, type the old password, then tap Done.
Password-protected spreadsheets stay protected when you share them using iCloud, so your collaborators will need the password to open the spreadsheet. If the spreadsheet is already being shared on iCloud, you can add, remove, or change a password in Share Settings.
Spreadsheets can have only one password, so if you change the password when you share the spreadsheet, that becomes the spreadsheet’s only password.
Note: Adding a password to a spreadsheet doesn’t encrypt the file.