1.3GHz processor, Windows XP (SP3), Windows 7, or Windows 8. It requires roughly 1.9GB of hard-disk space and 512MB of RAM (1GB recommended).
If you have a valid serial number for Adobe Acrobat X Pro, you can download the official installer directly from the Adobe website. Adobe maintains a repository of older products for licensed users. adobe acrobat x pro download
However, if you have a legitimate legacy license and a compatible older machine, here is what you need to know. Windows XP (SP3)