You might have been able to avoid this conundrum when you created the Acrobat installer by using the following Property that is documented in the ETK.
| PDF Ownership | 10.0 & later | LEAVE_PDFOWNERSHIP | For new installs. YES prevents the new installation from taking over PDF ownership. NO allows the new install to own opening PDFs. May interact with IW_DEFAULT_VERB for some versions. It is often used for silent installs where the user should not be asked to select a default PDF viewer. For 11.0 and later, do not use this property when OWNERSHIP_STATE has a value of 1 or 2. Note: This property is deprecated on Windows 10 machines and DISM-GPO configuration methods must be used. |
It cannot be used in an Update scenario.