There are two levels of Microsoft PowerPoint password protection, one to open the presentation and one to enable making changes to presentation. Let's check both of them.
You would expect the North Pole to be all white, covered in snow and cold, but not at the moment, as the North Pole literally turned into a lake. Global warming or natural process?
If you are afraid your friends, kids or any other person you are borrowing your iPad to, might delete an app by mistake or even intentionally, you can enable restrictions on individual all of the apps.
It's highly recommended to protect your computer against Virus, Malware, Spyware and other potential threats. Microsoft Security Essentials is one of the better, free solutions.
If you don't have installed program for editing PDF documents on your computer, then you can use web application PDFescape which allows you to edit your documents in your browser.