VB .NET - Attempting to change the icon (image) of a PDF button programatically?

Hey guys,
 
I am using the following code to populate PDF fields on a template PDF form I have.. the form also has a company logo in the top left that used to be un-changeable in the PDF form... but now I want to change it, so I deleted the logo image and replaced the image with a button on the form. I need to change the button's icon property programmatically using vb .net How do I do that? :
     
Dim pdfReader As New PdfReader(pdfTemplate)
Dim pdfStamper As New PdfStamper(pdfReader, New FileStream(newFile, FileMode.Create))
Dim pdfFormFields As AcroFields = pdfStamper.AcroFields
Dim TempPDFFilename As String = newFile
   
pdfFormFields.SetField("LeaseDate", vsLeaseDate)
pdfFormFields.SetField("Lessor", vsLessor)
pdfFormFields.SetField("Lessee", vsLessee)
pdfFormFields.SetField("Suites", vsSuites)
pdfFormFields.SetField("Floors", vsFloors)
pdfFormFields.SetField("RentableSqFt", vsRentableSqft)
pdfFormFields.SetField("UsableSqFt", vsUsableSqft)
pdfFormFields.SetField("PremisesLocation", vsPremisesLocation)
pdfFormFields.SetField("PremisesCity", vsPremisesCity)
pdfFormFields.SetField("PremisesCounty", vsPremisesCounty)
pdfFormFields.SetField("PremisesState", vsPremisesState)
pdfFormFields.SetField("PremisesZipCode", vsPremisesZipcode)
pdfFormFields.SetField("LeaseBaseRent", vsLeaseBaseRent)
pdfFormFields.SetField("LeaseCommencementDate", vsLeaseCommencementDate)
pdfFormFields.SetField("LeaseExpirationDate", vsLeaseExpirationDate)
pdfFormFields.SetField("PaidSecurityDeposit", vsPaidSecurityDeposit)
pdfFormFields.SetField("AddendumBody", vsAddendumBody)
pdfFormFields.SetField("PremisesAddressFull", vsPremisesAddressFull)
pdfFormFields.SetField("LeaseProratedBaseRent", vsLeaseProratedRent)
pdfFormFields.SetField("LessorLine2", vsLessorLine2)
pdfFormFields.SetField("LesseeLine2", vsLesseeLine2)
pdfFormFields.SetField("LessorNamePrinted", vsLessorNamePrinted)
pdfFormFields.SetField("Lessee1NamePrinted", vsLesseeNamePrinted)
pdfFormFields.SetField("LessorTitle", vsLessorTitle)
pdfFormFields.SetField("Lessee1Title", vsLesseeTitle)
pdfFormFields.SetField("Lessee2NamePrinted", vsLessee2NamePrinted)
pdfFormFields.SetField("Lessee2Title", vsLessee2Title)
pdfFormFields.SetField("Lessor2Title", vsLessor2Title)
pdfFormFields.SetField("LessorAddressLine1", vsLessorAddressLine1)
pdfFormFields.SetField("LesseeAddressLine1", vsLesseeAddressLine1)
pdfFormFields.SetField("LessorAddressLine2", vsLessorAddressLine2)
pdfFormFields.SetField("LessorAddressLine2", vsLessorAddressLine2)
pdfFormFields.SetField("Lessorworkphone", vsLessorWorkPhone)
pdfFormFields.SetField("Lessorfaxphone", vsLessorFaxPhone)
pdfFormFields.SetField("Lessorhomephone", vsLessorHomePhone)
pdfFormFields.SetField("LessorCellphone", vsLessorCellPhone)
pdfFormFields.SetField("Lesseeworkphone", vsLesseeWorkPhone)
pdfFormFields.SetField("Lesseefaxphone", vsLesseeFaxPhone)
pdfFormFields.SetField("Lesseehomephone", vsLesseeHomePhone)
pdfFormFields.SetField("LesseeCellphone", vsLesseeCellPhone)
pdfFormFields.SetField("LessorEMAIL", vsLessorEMAIL)
pdfFormFields.SetField("LesseeEMAIL", vsLesseeEMAIL)
pdfFormFields.SetField("LessorTIN", vsLessorTIN)
pdfFormFields.SetField("LesseeTIN", vsLesseeTIN)
pdfFormFields.SetField("LessorBrokerName", vsLessorBrokerName)
pdfFormFields.SetField("LessorBrokerAddressLine1", vsLessorBrokerAddressLine1)
pdfFormFields.SetField("LessorBrokerAddressLine2", vsLessorBrokerAddressLine2)
pdfFormFields.SetField("LessorBrokerWorkPhone", vsLessorBrokerWorkPhone)
pdfFormFields.SetField("LessorBrokerFaxPhone", vsLessorBrokerFaxPhone)
pdfFormFields.SetField("LessorBrokerHomePhone", vsLessorBrokerHomePhone)
pdfFormFields.SetField("LessorBrokerCellPhone", vsLessorBrokerCellPhone)
pdfFormFields.SetField("LessorBrokerEMAIL", vsLessorBrokerEmail)
pdfFormFields.SetField("LessorBrokerTIN", vsLessorBrokerTIN)
pdfFormFields.SetField("LesseeBrokerName", vsLesseeBrokerName)
pdfFormFields.SetField("LesseeBrokerAddressLine1", vsLesseeBrokerAddressLine1)
pdfFormFields.SetField("LesseeBrokerAddressLine2", vsLesseeBrokerAddressLine2)
pdfFormFields.SetField("LesseeBrokerWorkPhone", vsLesseeBrokerWorkPhone)
pdfFormFields.SetField("LesseeBrokerFaxPhone", vsLesseeBrokerFaxPhone)
pdfFormFields.SetField("LesseeBrokerHomePhone", vsLesseeBrokerHomePhone)
pdfFormFields.SetField("LesseeBrokerCellPhone", vsLesseeBrokerCellPhone)
pdfFormFields.SetField("LesseeBrokerEMAIL", vsLesseeBrokerEmail)
pdfFormFields.SetField("LesseeBrokerTIN", vsLesseeBrokerTIN)
pdfFormFields.SetField("Lessor_PaymentAddressName", vsLessorPaymentAddressName)
pdfFormFields.SetField("Lessor_PaymentAddressLine1", vsLessorPaymentAddressLine1)
pdfFormFields.SetField("Lessor_PaymentAddressLine2", vsLessorPaymentAddressLine2)
pdfFormFields.SetField("Lessor_PaymentAddressLine3", vsLessorPaymentAddressLine3)
pdfFormFields.SetField("Lessee2Phone", vsLessee2Phone)
pdfFormFields.SetField("PremisesAddressFULL", vsPremisesAddressFull)
pdfFormFields.SetField("UserInfoStamp", "LeaseGen Version: " & VERSNUM & " " & "GENERATED " & Today & " BY: " & MDIParent1.CURRENTUSER)
  
pdfStamper.FormFlattening = True
 
' close the pdf
 
pdfStamper.Close()
 
'open pdfviewer and show temp file
FrmPDFViewer.Show()
FrmPDFViewer.AcroPDF1.src = TempPDFFilename
Exit Function