When you create a password, write it down and keep it in a secure place. If you lose the password, you cannot open or gain access to the password-protected presentation. Microsoft cannot provide assistance for opening or modifying a presentation whose password you don't remember.
Note Setting a modify password allows others who do not know the password to view the presentation, but prevents them from making any changes to the presentation.
Tip
To create a long password ù up to 255 characters ù on the Security tab, click Advanced, select an encryption type, and then in the Choose a key length box, use the arrows to select the number of characters you want to use for the long password.