This was why I suggested using Foxit Reader.
I guessed that
Did you know that Foxit had also been vulnerable/targeted in the past - if there's a vulnerability in a popular software, *someone* will try to exploit it.
Rick, it's very important to ensure you're running a supported and updated Windows version, most of the recent MS patches for the Windows graphics subsystem have been specifically to prevent these exploits from infecting Windows and they are the main reason MS took on the task of issuing Flash updates for W8/10 and IE/Edge.
Same for all your Internet facing software - use the latest, patched versions.
Don't open pdfs in a browser, download them first. If they came via email, vet them before deciding whether to open them in your (patched) pdf reader of choice.