I finally managed to add the controls via the 3rd method you suggested. After adding the control to my VB form, and test running the app, I get the following error:
"Spire.PdfViewer.Forms.PdfDocumentViewer, Spire.PdfViewer.Forms, Version=2.12.0.3335, Culture=neutral, PublicKeyToken=663f351905198cb3"
file: licenses.licx