When a user locks their profile, non-friends will not be able to share or download their profile picture, cover photo. They can’t even zoom in on these pictures. Strangers also won’t be able to see photos and posts you’ve shared on your timeline, including old and new photos and posts.
If a stranger wants to take a screenshot, they’ll get a message “This app doesn’t allow screenshots”. If they want to record the screen, it’s all black. However, this feature is currently faulty because there are still cases where the personal page is locked but others can still take screenshots.
To lock a profile page, follow these steps: Settings => Personal page protection lock => Enable feature after reading its options. If you can’t lock your profile, you can still control your privacy in other ways, through your privacy settings.