Solution: Update Acrobat to the latest version
The problem is fixed in the August 19, 2020 hotfix patch of Acrobat. The patch is automatically applied to all existing installations of Acrobat. To update your Acrobat manually, choose Help > Check for updates and follow onscreen instructions to apply the latest patch.
Problem
Installing the latest version of Acrobat or updating Acrobat to the latest version (20.012.20041) in presence of AutoCAD 2018 results in the following warning on every launch of AutoCAD 2018:
Versions of AutoCAD impacted: All versions of AutoCAD 2018 (64-bit)
OS impacted: Windows 10, 8, and 7
Workaround
Select the Load all applications option from the warning dialog to launch AutoCAD. You can continue to use the Acrobat ribbon in AutoCAD to convert AutoCAD files to PDF. Other functionalities of AutoCAD are also not impacted.
