Adobe Acrobat 9 on a PC with Windows 7 (64-bit)

acrobat 9 doesn't qualify for an upgrade, but if it did you would not need to install it prior to installing the upgraded acrobat, Plans and pricing | Adobe Acrobat DC

with all adobe upgrades, if a qualifying product is not detected by the installer you are offered a dropdown from which to select the qualifying product.  you are then required to enter your serial number for the qualifying product before installation of the upgrade continues.