Error 11020 frequently points to a corrupted MSI database. Use the Windows Installer CleanUp utility (legacy but effective).
To avoid library conflicts, remove any existing versions of Adobe Reader or older Acrobat Pro versions via the Control Panel > Programs and Features . adobe acrobat xi pro 11020 install
: Enter your 24-digit serial number when prompted. Note that standard online activation may fail if Adobe's legacy servers are offline. Key Compatibility and Security Notes adobe acrobat pro 11.0 update (acrobat XI pro) | Community Adobe Acrobat XI Pro 11