jBPM5 is a generic framework to build business processes. What you are asking is a customization. We can provide a generic work item or a human task to a related document, that's totally understandable, but it's not there right now. If you code it the whole community can re-use it, it's a just write one use it forever situation.
If you want assistance writing that, let us know.
Greetings
No pain no gain my friend!