Q: Resetting an Macbook Pro

You may have to try to download the replacement OS X from the Apple server with the same

Apple ID account the computer was purchased with, because that's where it'd be located;

the older OS X is not a download from the App Store by itself; and the original OS X that

was included with the computer is what it should have. Then, if the 'new owner' wants to

upgrade past that, they'd go with their Apple ID & consider if the latest OS X will work in it.

You could take the computer to an Apple Store with Genius bar (contact ahead, set an

appointment so as to reserve to a time frame for this, and your visit) to have them help.

Their internet connection is also usually much better than a residential connection...

Also, they'd probably suggest you to use an Ethernet connection to install an OS X if

you're doing it, because your wi-fi is many times slower and this will take many hours.

Several suggested methods of reinstalling the original OS X exist in official online articles.

Some pertain to OS X Recovery, others in 'how to install' articles. The one I've been not

able to find, says exactly what the original owner needs to do, so the new owner can just

start up the computer as though nobody else owned it, and on boot-up enter their own

information to personalize the OS X and set up the admin user account, & so on.

• What to do before selling or giving away your Mac - Apple Support

• How to prepare your mac for sale* (or give away) thesafemac:

http://www.thesafemac.com/how-to-prepare-your-mac-for-sale/

• How to reinstall OS X on your Mac - Apple Support

*a tiny bit from 'thesafemac - how to prepare your mac for sale' says this detail:

"Once the erase is finished, quit Disk Utility and proceed with reinstalling the system. Eventually,

the system will get to a point where the Setup Assistant will open, allowing you to set up the new

system. At this point, quit Setup Assistant and shut down the computer. This way, when the buyer

turns on the computer for the first time, it will act like a new machine, and will allow them to go

through the setup process themselves."

So some of the information may vary depending on the actual process desired. As the

holiday weeks are upon us, the Apple Store with Genius may need to be put off awhile.

But it never hurts to ask anyway: https://www.apple.com/retail/geniusbar/

You can use the online page or contact the local retail official Apple Store about Genius.

In any event...

Good luck & happy computing!