If you want to convert a PDF file to CAD, you need to be aware that there are two types of PDF file, raster and vector.
Internally, the two types of PDF file are quite different. Converting them to a CAD file format such as DXF or DWG requires different processes.
If your PDF file was created by scanning a drawing, it will be a raster PDF file. A raster PDF file is essentially a raster image - usually TIFF or JPEG - held within a PDF wrapper. Because it is a raster image, it needs to be converted to CAD using raster to vector conversion.
If your PDF file was created by saving PDF from a CAD program, it will most likely be a vector PDF file. Unlike raster PDF files, vector PDF files already contain vectors, although not in a format that most CAD programs can understand. To convert a vector PDF file to CAD you need a vector PDF to CAD converter.
Here are two ways to tell if your PDF file is raster or vector:
1. Load your PDF file into Adobe Reader, then click on it.
If nothing happens, the PDF file is vector.
If the drawing is highlighted in blue when clicked on, it is raster.
Note that this does not work in all versions of Adobe Reader.
2. Load your PDF file into Adobe Reader, then zoom into it.
If lines and arcs continue to appear smooth as you zoom further and further in, the PDF file is vector.
If lines and arcs begin to look "stepped" as you zoom further and further in, it is raster.
For more information on PDF files, see SCAN-TO-PDF: Benefits and Considerations.