Hello,
Thank you for your further feedback.
You need to reference Spire.Pdf.Asp.dll, Spire.License.dll, and Spire.PdfViewer.Asp.dll from same floder( ASP.NET4.0, according to target framework), also Spire.Pdf.dll and Spire.Doc.dll from same floder( NET4.0).
Sincerely,
Caroline
E-iceblue support team