Do you have a legitimate Adobe Acrobat XI Pro serial number (purchased before 2017)? You may still be able to download the 11.0.20 update legally.
If you have a valid serial number, follow this step-by-step guide: adobe acrobat xi pro 11.0 20 download
Adobe Acrobat XI Pro was released in late 2012 and reached its “end of life” (EOL) in October 2017. The specific sub-version, 11.0.20, was one of the final patch updates released in 2017. This update primarily addressed security vulnerabilities and minor bug fixes. Do you have a legitimate Adobe Acrobat XI
Websites offering "free downloads" of commercial software often bundle their installers with: Even if you see a valid-looking serial number,
Even if you see a valid-looking serial number, the installer itself may be compromised.