It appears that the latest release of Adobe Acrobat Reader DC has caused an issue when a PDF is opened in an ActiveX control, such as the control that the CHM Viewer (hh.exe) uses. We create a CHM file that opens an embedded PDF so the users don't have to print topic-by-topic, and now they can't open the PDF to print. A CHM file is part of the requirements, so we can't send them the PDF directly. We can recompile the CHM to open the PDF in a new window, but it will only open in Internet Explorer, which the users aren't allowed to use. I tried uninstalling IE locally, and now the new window link doesn't do anything.
I'm requesting that the CHM Viewer be upgraded to work without relying on ActiveX controls. Since IE11 support will be dropped from M365 apps in August, I hope that the CHM viewer can be upgraded as well.