How do I start the installed version of (Continuous)

I have been happily using Acrobat DC Pro for at least a decade and have always been amazed at its efficiency and effectiveness. Until this week. All I wanted to do was combine two appropriate documents to create one new one. I haven done that before many times. It would not do it and told me I had a new version of DC on my computer that apparently is DC (Continuous) which I have to use. First problem then was I had never heard of this version and certainly didn't install it. I went hunting in my apps and found I had 64 bit version installed in my computer (1.14GB) in the list of installed apps.  It was dated May this year. Okay, so perhaps it came in as an update to DC (2015). The issue now is I can't find any way to start Continuous to discover how to do a job that I could - until this week - do easily with my good old DC version 1118-1008-8043-9167-4006-4905. Please help me start this Continuous version, or tell me if I can get rid of the upgrade so my earlier version works as usual.