how do you use it.

You use it to view and read PDF files.

okay thank you very much should i back it up.

No, it's a program, not a file, and something you can download and install from Adobe any time.

okay thank you very much.

By the time you'd need the backup, they'll have probably updated six times to version XVI instead of X.

okay thank you guys very much, i wish they would start putting in window 8.

None of the operating systems - XP, Vista, Windows 7, Windows 8.1 - none of them include the Adobe Reader. If you buy a brand name computer like HP or Dell or whatever, they will usually load the computer up with 3rd party software such as the Adobe Reader. But a straight installation of an operating system does not include software from other companies. You have to download and install it yourself.

okay thank you guys very much.