We've just tested here on Win 10 with MS Office 2016, 32-bit and could not reproduce the issue. It doesn't appear to be specific to any version of MS Office or Windows. or the architecture of Windows/MS Office.
One final suggestion, before escalating the issue further, please try to re-register the DLL for the add-in:
1) type CMD into the Windows Start Menu, then right click the CMD and select "Run as Administrator" (Please note, running as admin is essential, otherwise the registration will fail!
2) Type the following and hit enter (architecture specific):64-bit Office:
regsvr32 "C:\Program Files\Tracker Software\PDF-XChange 6\PXCOfficeAddin6x64.dll"32-bit Windows/Office:
regsvr32 "C:\Program Files\Tracker Software\PDF-XChange 6\PXCOfficeAddin6.dll"
If successful, you should see this message:
If not successful, or if that doesn't help, let me know!
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