If you are still using XI, you cannot update it to a newer version of itself . Instead, you must migrate to a supported product:
It will not reach a secure state.
Prior to October 2017, whenever a "zero-day" exploit was discovered (a vulnerability known to hackers but not yet known to the developer), Adobe would rush to release an update. If you were a diligent user, you downloaded the patch, and your system remained secure. adobe reader xi update
If you are unsure whether you are running Adobe Reader XI or a newer edition, follow these steps: If you are still using XI, you cannot