I want to download an ISO for my friends computer. But all he is eligible for is Windows 10 home edition. Will the ISO that I download on my Windows 10 Pro work for his?
I believe they are different. They haven't contained the different versions of Windows in the same DVD since Vista, and it's a shame because it was a great idea. Download the Windows 10 ISO tool here, and you can select the appropriate version, and you need to unfortunately download both the Home for him and Pro for yourself. One benefit is that I believe the ISO will now have the new "fall update" version 1511.
They are indeed different. You can use the Media Creation Tool to download the correct install (either to the machine you need to install on or to a USB stick for install on a different device) Available Here