To install Adobe Acrobat 9, use the installation media that came with the software purchase. Alternatively, download a replacement installer from the Acrobat Help website. A software license activation occurs during installation and requires a serial number.
As of 2015, only the Windows edition of Adobe Acrobat 9 has replacement installers available online for two versions: Standard and Professional. When the download is complete, click the executable file and follow the onscreen instructions. The software requires a computer that has at least a 1.3GHz processor, 512 MB of RAM and 1024-by-768 screen resolution. The computer must run Microsoft Windows XP Home, Internet Explorer 6.0 or later versions. Adobe Acrobat 9 may not run properly on more recent operating systems, in which case Acrobat X and XI are more appropriate to use.
The serial number is necessary for product registration, updates and upgrade plans. To find the serial number, inspect the product box or prepaid card that came with the purchase. Alternatively, ask the reseller to send an email with a redemption code and submit the code to Adobe online to get a serial number. Users who already registered Adobe Acrobat 9 or purchased it directly from Adobe.com may find the serial number in their online Adobe accounts, specifically in the Plans & Products section on the Manage Accounts page.