I got my copy of Office 2013 Pro via an employer Home Use Program (HUP) download. When I performed a clean install upgrade from Win 7 to Win 10, I had to reinstall it. YES, I had to be online to install it since the only file I had on my hard drive was the Office 2013 installer EXE file which is less than 1 MB in size. The installer filename starts with "Setup.x86.en-US_ProPlusRetail..." with the remaining characters being the product key. As I recall, it took about 30 - 45 minutes for the download/installation process to complete at my mediocre connection speed. During the installation, all applicable updates to Office 2013 Pro were also installed.