Users can install http://www.wintopo.com/wintopo-freeware.htm free edition.

Optionally, it's also possible to use INKSCAPE freeware from https://inkscape.org , drag-and-drop a PDF vector file in to a Inkscape session, and then save it as dxf.

Notice that only PDF vectored entities can/will be converted.

Current CMS IntelliCAD 9.2 PE or PE PLUS is able to import .PDF files containing vector entities. Entities will be imported as lines, polylines or splines. Use IMPORT or PDFIMPORT command and select .PDF file format.
Select the PDF page to import, a insertion point, scale factor and rotation angle. Import feature may not import all entities.