I do this frequently for preliminary site evaluations.
Be aware though that GIS data does NOT match actual survey data.
There may be significant discrepancies and I add a disclaimer to any drawing using GIS as base site data.
My method is to first take a screen capture of the site in GIS.
I use SnagIt for this.
This creates a .jpg file that can be imported into SoftPlan.
After importing the jpg it must be resized.
Most GIS sites have a "measure" tool that allows you to determine length of property lines.
I use the longest straight side to improve accuracy.
Then use Edit > Adjust size and select the imported jpg image.
The adjust size dialogue box opens and you have a choice of scale or length.
Choose length and import the length of the property line you have measured.
Finally click on one end of the property line and then the other and the entire image will be resized.
Once again, this is a very crude system which can not replace an import of a stamped Dwg or Dxf site survey.
But it is a very useful tool for preliminary review of site conditions.
Most GIS sites have a topo overlay function which can also be used to evaluate grade change on the lot.
My experience has shown that the topo information must also NOT be taken as actual site conditions.
There may have been grade changes made after the GIS data was established.
Steve