McAfee uninstalled my client's antivirus software

That doesn't seem right.

As an extra layer of healthy paranoia and precaution, I would've backup all data, zeroize the entire hardrive, repartition the hard drive, format the hard drive, then install a fresh copy of the operating system, and last, re-install the programs.

But if computer security is something that your Client really don't care about too much, at least I would've also suggested to uninstall   Adobe Reader DC using the Acrobat Cleanup and Repair tool.

Then run the .msi setup program again for Adobe Reader , but this time unchecking the option to install McAfee.

Yeah. It is a big problem. I faced such problems on the phone when I've tried to install real spy apps. The problem was solved by deleting both antiviruses and all of their files and installing the antivirus software I used before. 

Ouch!  I have never been a fan of that co-installation option... but apparently there's a good reason it's there.  I suspect it's a financial one.  I have also seen posts by the hundreds over the years asking how to fully remove McAffee products so they don't keep badgering for subscription money.  I believe McAffee intentionally buries their roots deep into a user's system.  Yeah, antivirus has to work in a deep level, but I don't care for their approach here, personally.

Good luck! 

Dave