The PDF preview in Outlook 2016 doesn’t work anymore with PDF xChange editor build 7.0.323. You should be able to re-register the dll, but that doesn’t seem to work.
regsvr32 /s "C:\Program Files\Tracker Software\Shell Extensions\XCShInfo.x64.dll"
For now the only option is to downgrade or wait for the next update, Tracker Software has found the cause and it should be solved in build 7.0.323.1.
