Allowing multiple files to be processed through one module - vb.net

Question

I've created a program to modify security settings of a .pdf file.
This works fine for one file - but I want to allow editing multiple .pdf's with the touch of one button and am struggling to make it work.
I have pasted the code for my GUI below, "Modify_PDF" is the module that runs the pdf security modification code. Is it possible to run multiple files through this module from here?
Dim source_file As String = ""
''' Handles clicking of the 'Open file' button
Private Sub open_button_Click(sender As System.Object, e As System.EventArgs) Handles open_button.Click
Dim input As FileStream = Nothing
'Set filter to only allow compatible files
OpenFileDialog.Filter = "PDF documents (*.pdf)|*.pdf"
'Allow multiple files to be opened
OpenFileDialog.Multiselect = True
'open the file selection dialogue
If OpenFileDialog.ShowDialog() = System.Windows.Forms.DialogResult.OK Then
Try
input = OpenFileDialog.OpenFile()
Catch Ex As Exception
MsgBox("Error opening file: " & vbCrLf & Ex.Message)
Finally
'Check this again to ensure no exception on open.
If (input IsNot Nothing) Then
input.Close()
End If
End Try
If input IsNot Nothing Then
source_file = OpenFileDialog.FileName
If Modify_PDF.process_file(source_file, "") Then
PDF_name.Text = Path.GetFileName(OpenFileDialog.FileName)
input.Close()
modify_button.Enabled = Modify_PDF.process_file(source_file, "") 'Allow report to be created if processing succeeds
End If
End If
End If
End Sub
''' Handles clicking of the 'Modify PDF' button
Private Sub generate_button_Click(sender As System.Object, e As System.EventArgs) Handles modify_button.Click
Modify_PDF.modify_pdf(source_file, source_file, "")
End Sub

Answer 1

Try it like this:
If OpenFileDialog.ShowDialog() = System.Windows.Forms.DialogResult.OK Then
Try
For Each FileName as String in OpenFileDialog.FileNames
'Do something with the filename here
Next
Catch ...