Hi Larry,
Thank you very much for your kind words!
Long story short, we are actually using a custom code to add thumbnail images to PDF files – so they are not automatically generated, we created them, uploaded and linked to the PDF files via a custom meta field (so it is a very annoying solution).
We hoped to add an automatic script to extract images from PDF document first pages to the current release, but it turns out it is actually not possible out of the box with WordPress and PHP.
The web server requires the ImageMagick extension and it needs to be reconfigured to work properly. We have a working code to extract thumbnails, but it requires an extra step to change the back-end ImageMagick policy file configuration – and that is problematic, because it requires root access to the server via SSH and most users do not (and should not) make changes there. Unfortunately this is the simplest possible way.
The good news is, that we are going to integrate this code to the upcoming release for sure. Then a knowledge base and blog article will be created as a step by step guide on how to configure the ImageMagick on the back-end servers. This update is scheduled for the next weekend.