Version 5.2 was specifically released to support the 64-bit version of Adobe Acrobat DC. Older versions of the plug-in (5.0 and earlier) will not work with 64-bit Acrobat.
If you already own Quite Imposing 4 or an older version, the update process (the "upd" part of your search) is straightforward. quite imposing 5 serial number upd
: Supports modern systems including macOS 10.15 (Catalina) and Windows 7 or above, running in Acrobat DC, 2017, 2015, and older versions. Enhanced N-Up & Creep Version 5