Important presentations need to be kept secret until they're ready to be shared. For this reason, Apple's Keynote presentation software allows you to lock a slide deck with a password.
Here's how to set a password to lock a Keynote presentation.
1. Click File.
2. Select Set Password.
3. Enter a password, enter it again and click Set Password.
You've set a password that will need to be entered to open your Keynote presentation.