As a workaround, you can build this kind of logic into your workflow. Basically, you would search ahead to see if that document already exists. If so, "download" the electronic document and attach it to the existing one. If not, replicate. Here's a simple screenshot; a few notes:

• Make sure version control is on for the destination repository
• This is only for electronic documents, like Word files, which I assume is your case
• I no longer have my fully fleshed out WF with this logic, just the shorthand testing I kept for my reference; when testing you may find that you need to enhance this a little