If you are an enterprise user maintaining an older workstation, or if you have a specific legacy workflow that requires XI, ensure you download the installer directly from your Adobe account history, keep the machine offline if possible to mitigate security risks, and keep a physical backup of the installer and serial key.
on October 15, 2017. While Adobe no longer provides security updates or technical support for this version, users with existing perpetual licenses can still download and install it by following specific procedures. 1. Locate Your Serial Number download install adobe acrobat xi standard