Thanks Stefan, I'm using the latest PDF24 11.7, but have checked and it appears that I'm running 32bit Office 19 applications, so this is possibly why I can't get the preview working. Not sure if there...

I've started using PDF24 Creator and am wondering if it is possible to enable Previews in Outlook PDF attachments or do I have to download Adobe Reader?  At the moment Outlook is telling me "This file...