To turn a PDF into a DWG/DXF follow these instructions:
1.) Open NanoCAD and from the Insert tab select Import and then PDF.
2.) Then path out to the PDF file you would like to convert and choose the page/pages you would like.
3.) Next, select the settings shown below from the Import dialog window.
4.) Then, click OK.
5). Now you can save the file and import it into iModel by going to Layout\Import DWG/DXF.