The workaround that I use is to print the PDF to DWF using the DWF writer printer, then copy the DWF to the clipboard and use the special paste function in the edit menu in AutoCad to paste the DWF in as a autocad entities. This works OK, but there is a few things that you'll need to clean up. For instance, all the text is individual pieces of text. I use the express tools
and convert all the text to mtext to solve this. The other real annoying thing is that if the PDF has any images embedded in it, they will not paste in as autocad entities. You'll have to paste them in a image entities. Mark tells me, he has a way to deal with this though.