It depends on how you create the document  workspace?

1. If you create the document workspace  from an existing document, then
by default, you will only have one document in that workspace. But you
will have the ability to upload more files. The only downside is that
all the new files that you uploaded, you will not have the 'Publish to
Source Location' feature.

2. If you create the document workspace from the documents and lists
page, then you can upload as many files as you want.

If I create a document  workspace using the second option I
won't have the Publish to Source location either, right? Or is there
a way when you upload documents where you can post them back to the
Source location?

Nope, you lose that functionality. I don't know of any way to bring in
multiple files and to have this feature also.

Maybe somebody in the newsgroup might know how to do this
programmatically.