PdfFormatProvider provider = new PdfFormatProvider();
provider.ImportSettings.DocumentUnhandledException += this.ImportSettings_DocumentUnhandledException;

private void ImportSettings_DocumentUnhandledException(object sender, DocumentUnhandledExceptionEventArgs e)
{
    if (e.Exception is InvalidGraphicOperandsCountException)
    {
        e.Handled = true;
    }
}

This exception was originally thrown at this call stack:
    Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Elements.DocumentStructure.DocumentCatalog.CopyEmbeddedFilesTo(Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Import.Parser.PostScriptReader, Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Import.IRadFixedDocumentImportContext) in DocumentCatalog.cs

   at Telerik.Windows.Documents.Core.Fonts.Type1.Type1Format.Type1FontSource.GetFontFamily()

        Dim signProp As New SignatureDataProperties
        signProp.ContactInfo = strContactInfo
        signProp.Name = strSignersName
        signProp.Reason = strReason
        signProp.Location = strLocation
        signProp.TimeOfSigning = DateTime.Now

        Dim signatureName As String = "EsignSignature"

        Dim signatureField1 As SignatureField = New SignatureField(signatureName)
        UseSignatureProperties = 1

        If UseSignatureProperties = 1 Then
            Dim sign1 = New Signature(certificate)
            signatureField1.Signature = sign1
            signatureField1.Signature.Properties = signProp 'THIS WOULD FAIL
        Else
            signatureField1.Signature = New Signature(certificate)
            signatureField1.Signature.Properties.ContactInfo = strContactInfo
            signatureField1.Signature.Properties.Location = strLocation
            signatureField1.Signature.Properties.Name = strSignersName
            signatureField1.Signature.Properties.Reason = strReason
            signatureField1.Signature.Properties.TimeOfSigning = DateTime.Now  'THIS WORKS
        End If