Obtain Vector Information from PDFs using Free Tools

Sometimes you will have access to a PDF file, but not to the original DWG.  Is there any way you can get the base vector data, such as lines and arcs, out of the PDF and back into a DWG?  Yes, there is - and it's free.

You will need 3 things:
Ghostscript or here
GSView
pstoedit (or Windows exe link here)

Download and install each of the above tools.  Make your life easy and stick with the 32-bit version of everything.

Once you have installed them all, open a PDF file using GSView.  GSView is usually located in  
C:\Program Files\ghostgum\gsview\gsview32.exe

With your PDF open, take the following steps:

1. Click on 'Media' and set the correct paper size.
2. Go to 'Edit' and click on 'Convert to vector format...'
   
3. At the resulting PS to Edit dialog box, choose dxf_s, and add the following Driver options:
   -mm -splineaspolyline -splineprecision 10
   (I have found these settings to work quite well)
   
4. Click OK.
5. Select the page in the next dialog (usually only 1), press OK, and then pick a place to save the DXF file.
6. Click Save.
7. Open in AutoCAD and scale to correct size.
8. Save as DWG.

If you have any problems, feel free to comment and I will try and help you out.  If you intend to import the DWG into Revit, keep in mind that Revit is not very impressed with very short lines.

Enjoy your PDF hacking!