The data that comprises a PDEPath object can be obtained from the PDEPathGetData() API. This is raw data containing the operands and operators (moveto, lineto, etc.) that draw the path.
If you are trying to recognize the shape of the PDEPath, attempting to locate all rectangles for example, you would need to parse the contents obtained from the PDEPathGetData() API.
It is important to keep in mind that specific shapes, such as rectangles, can be built in many ways, and using different operators. For example, you could build a filled rectangle with arect operator, or using four lineto operators followed by a fill.