You can use the pdf either as an overlay or as a trace reference on another storey level. I have stories identified as 3D Site Plan (for meshes) and 2d site plan.
Draw a mesh using the outermost points of the map. Select the mesh and directly over the known elevation points using the mesh single line method click once and then again. In the dialog "New Mesh Points" which will pop up select "Fit to User Ridges" and click "OK"
With the mesh still slected click on the newly created point and select elevate mesh point (Z) you can raise or lower the point elevation. I usually figure out and specify the Reference 1 Mesh Reference Plane (Options:Project References:Reference Levels) using the lowest elevation point offset from Project zero. This is usually a negative number represented by the difference between the actual mesh point z-level and the actual plotted elevation.
I have at times hand input complete master grading plans using this method when other methods aren't available although I will ask the surveyors xyz ASCII files and import surveyors data (Design:Place Mesh from Surveyors Data) as a mesh.
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