If you are using Designer to preview an XDP in the PDF Preview tab, you may receive the following error:
Wrong type parameter supplied to a PDS procedure
This error usually appears when the XML structure is no longer valid, i.e. it has been edited manually.
Open and save the form in Designer7.1, then it will correct any problems in the XML source, and work fine in PDF Preview.
Opening in Designer8.0 and later versions will also correct any issues.