Batch add text stamps as a new layer into PDF pages

Attribute VB_Name = "modVeryTest"
Option Explicit

Private Declare Function VeryStampOpen Lib "verywrite.dll" (ByVal sIn As String, ByVal sOut As String) As Long
Private Declare Sub VeryStampClose Lib "verywrite.dll" (ByVal id As Long)
Private Declare Function VeryStampAddRectWithLayer Lib "verywrite.dll" (ByVal id As Long, ByVal start_x As Long, ByVal start_y As Long, ByVal end_x As Long, ByVal end_y As Long, ByVal line_width As Long, ByVal text_color As Long, ByVal flagfill As Long, ByVal fill_color As Long, ByVal layer As Long) As Long
Private Declare Function VeryStampSetFunction Lib "verywrite.dll" (ByVal id As Long, ByVal func_code As Long, ByVal Para1 As Long, ByVal Para2 As Long, ByVal szPara3 As String, ByVal szPara4 As String) As Long

Sub Main()
    Debug.Assert False

    TestStamp "Test Data\Sample1_v1.6.pdf", 150, 150, 50, 50 ' Returns -1
    TestStamp "Test Data\Sample2_v1.6.pdf", 150, 150, 50, 50 ' Returns -1
    TestStamp "Test Data\Sample3_v1.5.pdf", 150, 150, 50, 50 ' Returns -1
    TestStamp "Test Data\Sample4_v1.5.pdf", 150, 150, 50, 50 ' Returns -1
    TestStamp "Test Data\Sample5_v1.7.pdf", 150, 150, 50, 50 ' Returns -3
    TestStamp "Test Data\Sample9_v1.6.pdf", 150, 150, 50, 50 ' No errors, but generates invalid output

End Sub

Private Sub TestStamp(Filename As String, ByVal X0 As Long, ByVal Y0 As Long, ByVal X1 As Long, ByVal Y1 As Long)

    Dim Processor As Long
    Dim Page As Long
    Dim ret As Long
    Dim ForeColor As Long
    Dim BackColor As Long
    Dim Outfile As String

    Outfile = App.Path & "\" & Filename & ".out.pdf"

    FileCopy App.Path & "\" & Filename, Outfile

    Processor = VeryStampOpen(Outfile, vbNullString)
    If Processor < 1 Then
        MsgBox "VeryStampOpen failed with " & Processor & " on file " & Filename
        Kill Outfile ' No need to keep the copy since we didn't do anything with it
        Exit Sub
    End If

    Page = 1

    ret = VeryStampSetFunction(Processor, 131, Page, 1, vbNullString, vbNullString)

    If ret <= 0 Then
        MsgBox "VeryStampSetFunction failed with " & ret & " on file " & Filename
        GoTo Cleanup
    End If