Handle the import of documents that have an invalid boolean value for the PrintScaling property of ViewerPreferences. The expected value of the /PrintScaling entry is a PDF name object:

/PrintScaling /None

/PrintScaling /AppDefault

When importing such documents, the following exception is thrown: 

InvalidCastException: 'Unable to cast object of type 'Telerik.Documents.Fixed.FormatProviders.Pdf.Model.Types.PdfBool' to type 'Telerik.Documents.Fixed.FormatProviders.Pdf.Model.Types.PdfName'.'