Mark up Drawings & User Defined References

We are currently using PDM Enterprise for data management. As we are starting to push models/drawings thru our workflows the question has come up, How to handle mark ups? The old way of course was to print out a hard copy, redline them, and give them back to the designer for changes. I would like to do the same thing within Solidworks. When I receive a notification that drawings need checked, I can open them (.slddrw) in E-Drawings, redline it and save it. I can then attach it to the drawing as a user defined reference. However, when I open the drawing (.slddrw) in Solidworks the attached file does not show up in the EPDM directory tree. It just shows the .slddrw and the .sldprt. When I send notification back to the designers that changes are required I want them to be able to open the .slddrw and be able to access the mark up from there. Has anyone tried this or something similar?

SolidworksSolidworks Pdm enterprise Pdm