close pdf in webbrowser control

I have a windows form application that I use to scan pdf and jpg documents. In the form I placed a webbrowser control to preview the scanned files.
All the file paths are displayed in a listbox and when the listindex change the webbrowser navigate to the file showing it.
Sometimes may happen that the scan isn't good or something like that so I need to delete the file, but when I select the file to delete it's opened in the webbrowser. I have no problem with jpeg, but with pdf it throws an exception telling that is impossible to delete the file because it's opened in another application.
I could kill the acrobat process but it's not the solution I want.
I tried to make the webbrowser navigate to about:blank and to dispose the webbrowser but with no luck.
Plus when I shut down the computer it always tells me that there is a document opened in acrobat and ask me if I want to close it. I think is related to my application.
Any help is appreciated

Private Sub cmsScanDeleteFile_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmsScanDeleteFile.Click
        Dim text As String = ""
        Select Case lstScan.SelectedItems.Count
            Case 1
                testo = "Are you sure you want to delete the selected file?"
            Case Is > 1
                testo = "Are you sure you want to delete " & lstScansioni.SelectedItems.Count & " selected files?"
        End Select
        Dim risp As String = MsgBox(text, MsgBoxStyle.YesNo)
        If risp = vbYes Then
 
            Dim cont As Integer = lstScan.SelectedItems.Count - 1
            Dim drows(cont) As DataRowView
            Dim x As Integer = 0
            For Each dr As DataRowView In lstScan.SelectedItems
                drows(x) = dr
                x = x + 1
            Next
            WebBrowser1.Stop()
            WebBrowser1.Url() = New Uri("about:blank")
            WebBrowser1.Dispose()
            For x = 0 To cont
                Call DeleteFile(drows(x).Item("id"))
            Next
            Call Save()
        End If
    End Sub
 
    Private Sub EliminaFile(ByVal id As Integer)
        Dim rf As dsat.AttivazioniScansioniRow = Me.Dsat.AttivazioniScansioni.FindByid(id)
        Dim file As String = ""
        If rf.Locale = True Then
            file = My.Settings.PercorsoLocaleAttivazioniWind & "\" & rf.NomeFile & rf.Estensione
        Else
            file = My.Settings.PercorsoAttivazioni & "\" & rf.PercorsoRelativo & "\" & rf.NomeFile & rf.Estensione
        End If
        Dim psi As New System.Diagnostics.ProcessStartInfo()
        psi.UseShellExecute = True
        psi.FileName = file
        If System.IO.File.Exists(psi.FileName) = True Then
            System.IO.File.Delete(file)
            rf.Delete()
            Me.AttivazioniScansioniTA.Update(Dsat.AttivazioniScansioni)
        Else
            Dim risp As String = MsgBox("Il file non è stato trovato nel percorso corretto, vuoi eliminarlo anche dal programma?", MsgBoxStyle.YesNo)
            If risp = vbYes Then
                rf.Delete()
                Me.AttivazioniScansioniTA.Update(Dsat.AttivazioniScansioni)
            End If
        End If
    End Sub

Select allOpen in new window