PDF's will not open in Adobe Acrobat Reader DC on my iMac running High Sierra?

First, thankyou for the reply. I am running Adobe Acrobat Reader DC, version 2018.011.20038 on my iMac

I use auto update and have confirmed that I have the latest update in place. I open PDF’s by clicking or ? double clicking on the icon. When I do, a new page opens and is totally black. I go back to the

email or website where the PDF is, click again, and get the same result, whether I do it 2, 3, or more times. This also happens sometimes when I try to open an ‘item’ in some website——for example, I subscribe to a medical CME site where I read some material, take a ‘pretest’, and then click on an option to take the ‘post test’….but it ‘opens’ with a black page. I had no problem with any of this until about a year ago. The same problem appeared on my MacAir about ? 3-4 months ago, which MAY have coincided with my upgrading the OS to High Sierra 10.13.3

I spoke at length today with AppleCare who could not fix this and said that he ‘saw online’ that Adobe was having 'problems of this type’ with High Sierra and may have a ‘patch or fix’——'so contact Adobe’, which I did and learned that the Forum is my only option. Thanks for any suggestions you might have.