Maybe it was once a bridge between apps, a loader for dreams in 64-bit light, or just a stub, a stubby guardian of features nobody asked for. Now it sleeps in shadowed folders, marked only by timestamps and small cruor of bytes.
I can provide step-by-step instructions for the specific fix that fits your situation. acrosup64.dll is not marked for installation
The error is a Windows Installer state mismatch, almost always caused by leftover Adobe installation data. It is fixable without reinstalling Windows. Maybe it was once a bridge between apps,