You can use passwords to help prevent other people from opening or modifying your presentations. Follow the instructions below:
1) On the [File] tab, click on [Info], then click on [Protect Presentation]. The screen below will be displayed:
2) Select one of the following options:
Mark as Final
This make the presentation read-only. Typing,
editing commands, and proofing marks are disabled or turned off. It prevent reviewers or readers from
making changes to the presentation.
Encrypt with Password
This allows you to set a password for the presentation.When you select [Encrypt with Password], the [Encrypt Document] dialog box appears. Type a password in the [Password] box.
Restrict Permission by People
You will have to use a Windows Live ID or a Microsoft Windows
account to restrict permissions. You can apply permissions via a
template that is used by your organization, or you can add permissions
by clicking [Restrict Access].
Add a Digital Signature
This is where you add a visible or invisible digital signature. Digital signatures are created by typing a
signature or by using an image of a signature to establish authenticity,
integrity, and non-repudiation.