Are you using the correct version of Adobe Reader for macOS Big Sur 11.6.
Click here,
https://get.adobe.com/uk/reader/otherversions/
Fill out the info on the left hand side.
Interestingly you say you are running Anti Virus software on macs
this is completely unnecessary on macs. There are no viruses that attack the mac.
All they do on a mac is use up system resources often flagging up files that you may be
encouraged to delete, often these files are system files and if deleted will degrade the
performance of your mac. The advice would be to get the full uninstall instructions
from the AV apps developer.
If you are running any other apps that claim to clean, speed up or protect your mac
they are unnecessary also, they just get in the way of the macs own management of
itself.
Read this,
Effective defenses against malware and ot… - Apple Community
