When trying to attach a PDF file to a DWG file you get the following information message:
And the following error message is displayed on message center:
and when you attach the PDF to a DGN and try to save as dwg format you will get the following alert message:”xx.pdf was not converted”. This file format is not supported in DWG work mode
So this functionality is not supported yet in the latest release of MicroStation SS3 but The alert when attaching PDF can be suppressed by editing the following configuration variable in the workmode.cfg file (by default C:\Program Files (x86)\Bentley\MicroStation V8i (SELECTseries)\MicroStation\config\system)
_USTN_CAPABILITY_DWG < +CAPABILITY_RASTER_ALL_TYPES variable.
Note: Of course it only works as a temporary attachment for one session.
When using Save As DWG in MicroStation CONNECT, an attached PDF file will become a PDF Underlay in DWG as PDF format is now supported in this version.
Taken from Help:
PDF underlay - Underlays are essentially raster references and are supported to the extent of the raster manager's capability of attaching a PDF file.