I agreed to load the Adobe Fill & Sign app via the 7-day free trial. Interestingly, I witnessed a number of "add on" apps in my Adobe programs. With great regret, the app never worked so I canceled the subscription before the end of the trial a couple days ago. Today I tried to use my faithful Adobe Acrobat X Pro to combine some files into a single PDF. The pop-up says I must use Adober Reader DC. Wrong answer! How do I get my Adobe Acrobat X Pro to work again?