Downloaded AA Pro trial version on my MAC it expired, I uninstalled it and I still cannot see pdf's

Can someone help?  I downloaded Adobe Acrobat Pro for a free trial on my MAC and realized how expensive it was and decided not to buy it.  I was unable to open up pdf documents so I uninstalled the Pro and now I can open pdf that are in my "documents" but some of the professional publications that I subscribe to have a web version of the publiation in a web pdf format and all I'm getting is a black screen.  Any thoughts suggestions?  I feel like AA has taken my computer hostage.  It shouldn't be like this! Help???  Thanks in advance!