Sorry, but your question is not clear. Do you:
1. Have a part in PDF format you want to try to add to a Solid Edge assembly? or
2. Are you trying to get a Part from Solid Edge output as a 3D PDF?
Assuming the 3D PDF file was created by you.....you'll need to edit your Solid Edge file to how you want it, then re-save, the part [or assembly] as an PDF, overwriting the existing one.
The SE viewer is a different thing all together, & regular [free] Adobe Acrobat Reader will open 3D PDF files just fine....which is kind of the point.
Design Manager Streetscape Limited
Solid Edge ST9 [MP3] Classic [x2 seats]