Getting Attachments into a Document Form

All

I am in need of a way to get various files into a Document Form as attachments. I have a list of documents which contains the files I want to attach and a means to convert this list to a map if necessary.

I am aware of the invokeDDX service but am unable to get it to work. Could somebody please clarify for me how to go getting these files into the Document Form as attachments?