Is Windows 8 Pro Upgrade 32 bit or 64 bit

Edit: No, the ISO contains either 32 or 64 bit version. Upgrade assistant downloads the correct version – 32 or 64 bit – depending on the hardware.

If you downloaded 32 bit version want 64 bit version, you have to download once again.
The ISO for 64 bit is slightly larger.

If you had 64 bit OS, then you want upgrade to 64 bit Windows 8.

The DVD with 32 bit version of Windows 8 contains only 32 bit version.
By installing 32 bit you limit yourself to using no more than 3.xx GB of RAM. If you have more RAM, you have to download 64 bit installer.

Otherwise you can use the DVD to upgrade as many systems as you want provided you have the key for each of them.

Windows 8 installs the version you are on at the moment. If you are currently running 32 bit, then when you Upgrade you will get the 32 bit version. If you are currently running 64 bit, then you will get the 64 bit version.