There are two issues here.
The first is that of Acrobat 8 Pro on Windows 7 x64. Although not originally designed for Windows 7 or for that matter any 64-bit version of Windows (there are components that are specific to the driver system of 32-bit versions of Windows and versions of Windows prior to Windows Vista), some Adobe users have been successful in installing, activating, and running Acrobat 8 Pro on Windows 7 x64 assuming that after installing Acrobat 8 Pro (which will install with some errors), you immediately apply the update to Acrobat 8.1! You did not indicate whether you even tried activating Acrobat 8 Pro. If you did try and didn't succeed, what error / message did you receive?
The second issue is that a perpetual license for a software product generally means that the software may be expected to run on the hardware and with the operating system environment available during the time in which the software version was current. Acrobat 8 was released in November 2006, over 10 years ago, when Windows XP was the current operating system and when Windows Vista was in preparation for release. A free update was provided for Vista support. But the perpetual license does not mean that the software vendor is going to provide free updates forever to provide support for new hardware and operating systems. If you want or need Acrobat Pro DC, you will need to either buy a new perpetual license for this version or subscribe to the software with a monthly payment. The subscription license includes automatic and no further charge updates to the latest version of the software as long as you subscribe.
- Dov