"%Doc[0]%" "%Doc[1]%"
That would be the proper syntax for the first two files in the List %Doc%; however, you should also just be able to put %Doc% in the Attachments and it will email all files in the list, if that is an option. %Doc% is a list of files, so the syntax of [0] is how you reference the first item on the list, then [1], [2], etc.
Best of luck!