How to add custom paper to windows system

Try this code.

Imports System.Runtime.InteropServices

Module Module1

    Sub Main()
        AddCustomPaperSize(Nothing, 
                           "Custom Paper Sample",
                           FormFlags.Printer,
                           10000, 10000, 
                           9000, 9000)
    End Sub

    Public Enum FormFlags
        User
        Buitin
        Printer
    End Enum

    Public Sub AddCustomPaperSize(printerName As String,
                                  formName As String,
                                  flags As FormFlags,
                                  width As Integer, height As Integer,
                                  imageWidth As Integer, imageHeight As Integer)
        Dim hPrinter As IntPtr
        If OpenPrinter(printerName, hPrinter, IntPtr.Zero) Then
            Dim formInfo As New FORM_INFO_1()
            formInfo.Flags = flags
            formInfo.pName = formName
            formInfo.Size = New SIZEL() With {.cx = width, .cy = height}
            formInfo.ImageableArea = New RECTL() With {
                .left = 0, .top = 0,
                .right = imageWidth, .bottom = imageHeight
            }

            If Not AddForm(hPrinter, 1, formInfo) Then
                Console.WriteLine("Failed to add form.")
            End If
            ClosePrinter(hPrinter)
        Else
            Console.WriteLine("Failed to open printer.")
        End If
    End Sub


    <DllImport("winspool.drv", SetLastError:=True, CharSet:=CharSet.Auto)>
    Private Function AddForm(hPrinter As IntPtr, level As Integer, ByRef form As FORM_INFO_1) As Boolean
    End Function

    <DllImport("winspool.drv", SetLastError:=True, CharSet:=CharSet.Auto)>
    Private Function OpenPrinter(pPrinterName As String, ByRef phPrinter As IntPtr, pDefault As IntPtr) As Boolean
    End Function

    <DllImport("winspool.drv", SetLastError:=True, CharSet:=CharSet.Auto)>
    Private Function ClosePrinter(hPrinter As IntPtr) As Boolean
    End Function

    <StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Auto)>
    Private Structure FORM_INFO_1
        Public Flags As FormFlags
        <MarshalAs(UnmanagedType.LPTStr)>
        Public pName As String
        Public Size As SIZEL
        Public ImageableArea As RECTL
    End Structure

    <StructLayout(LayoutKind.Sequential)>
    Private Structure SIZEL
        Public cx As Integer
        Public cy As Integer
    End Structure

    <StructLayout(LayoutKind.Sequential)>
    Private Structure RECTL
        Public left As Integer
        Public top As Integer
        Public right As Integer
        Public bottom As Integer
    End Structure

End Module

I've found it!!

The "type" of added form is set by "FormFlags".

AddCustomPaperSize(Nothing, 
                           "Custom Paper Sample",
                           FormFlags.Printer,
                           10000, 10000, 
                           9000, 9000)

So changing the line "FormFlags.Printer" is the solution:

• 0: "user defined"
• 1: "built-in"
• 2: "printer"

Now it works!!!

Thanks a lot!