Why wouldn't my PDF documents open in my newly installed Adobe Acrobat DC?

Hi, I've disabled my antivirus software and downloaded Adobe Acrobat DC but my PDF files will not open. 

Each time I try, I get the following message:  Adobe Acrobat Reader could not open (name of file) because it is either not a supported file type or because the file has been damaged (for example, it was sent as an email attachment and wasn't correctly decoded).

I have allowed the program to communicate through my Windows Firewall and still I am unable to open my PDF files.  Can someone please tell me why that is?

Thank you.

Felisa Wash