Hi there Janna,
Good news.
I just tested it .
It works 
I think by referencing you mean "association to Sales Order". If you associated to SO, it is ok.
The difference is just you need to use DocumentOutputRequestPreview_MD model dialog instead of Preview dialog.
And a different outport with different parameters.
As I have told before, please check the Preview outport of SalesOrderOWL or QAF.
Just copy the exact setting.
Let me know if there is any problem.
Cheers
Fred