Imports PdfSharp.Drawing
Imports PdfSharp
Imports PdfSharp.Forms
Imports System.Drawing

Public Class Form1
    Private mRenderEvent As PagePreview.RenderEvent
    Public WithEvents pdf As New RenderPdf

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'pg is pagepreview object in my main form

        Me.pg.SetRenderEvent(AddressOf pdf.render) 'delegate to sub render
        Dim pdfdocument As New PdfSharp.Pdf.PdfDocument
        Dim page As Pdf.PdfPage = pdfdocument.AddPage
        Dim gfx As XGraphics = XGraphics.FromPdfPage(page)

        gfx.DrawString("EXAMPLE TEXT", New XFont("Arial", 20), Brushes.Black, 10, 10)

        pdf.render(gfx)
        pdfdocument.Save("prova.pdf")
    End Sub

    Private Sub SetRenderEvent(ByVal renderEvent As PagePreview.RenderEvent)
        Me.pg.SetRenderEvent(renderEvent)
        mRenderEvent = renderEvent
    End Sub

End Class

'renderpdf
Public Class RenderPdf
    Public Sub render(ByVal gfx As XGraphics)
        '??? what code?
    End Sub
End Class

Public Sub renderPage(ByVal RenderGfx As PdfSharp.Drawing.XGraphics)

       Dim document As New PdfDocument(filename)
       Dim page As PdfPage = document.AddPage()
       page.Size = PageSize.A4
       RenderGfx = XGraphics.FromPdfPage(page)
       RenderGfx .DrawString("text", New XFont("Arial", 20), Brushes.Black, 20, 20)
       RenderGfx.Save()
End Sub