The DXF file format does not define physical dimensions using absolute measurements from a ruler. Instead it uses units which the user defines. When you create a PDF file from a CAD drawing, it is transformed to paper/print dimensions and the meaning of the original CAD units are lost but the xy relationship remains. As a result, pdf2cad can not restore the intended dimensions but it does preserve the scale. This means that you can calculate a scaling factor to apply during the conversion to achieve the size drawing you want. By default, pdf2cad uses 1mm(0,03937 inch) in the PDF = 1 unit in the DXF. You can change this under the DXF Options tab. You can also scale the DXF after import into your CAD application.
Tip: Sometimes pdf2cad delivers better precision and more accurate coordinates if you change one of the values in your pdf2cad.ini file. Please try setting the ctm_scale to 10.0 instead of 1.0 (default) in the pdf2cad.ini file. If this does not help, please send us the file to diagnose.