1. Make sure you have what you need
(a) Acrobat 9 install disk
(b) Acrobat 9 serial number
(c) If it was an upgrade, the old serial number
2. Install on the new computer, with disk and serial(s)
3. If you are told there are too many activations, contact Adobe. They might reduce the activation count. Or they might refuse, because it's out of support. This is a very uncertain area.
4. Manually install about 30 upgrades, as auto updating has failed.
Before installing it on the new machine, open Acrobat on the old machine, go to the Help menu and select Deactivate.