Have you ever needed to Xref (or reference) a PDF file? One way would be to save the PDF as a TIFF and reference the image. Of course there is the old way of inserting an OLE object referencing the PDF. Both have their drawbacks.
Here is another way. Download DWF Writer from Autodesk (it’s free), then open your PDF in Acrobat (reader is fine) and plot the PDF to a DWF using the DWF Writer print driver. Note that multi sheet PDFs are converted to a multi sheet DWF.
Then use the reference manager or the ._DWFATTACH command in AutoCAD to reference the DWF file. (The ability to reference DWF files was added in AutoCAD 2007).
Now if there was just some way to create a reference to each sheet in the DWF all at once rather than having to repeat the ._DWFATTACH command for each one.