Public Class Form1
 
    Dim myShowPdf As New frmShowPdf
    Dim ofd As New OpenFileDialog
    Dim WithEvents btnShowPdf As New Button
 
    Private Sub Form1_Load(ByVal sender As System.Object, _
    ByVal e As System.EventArgs) Handles MyBase.Load
        Me.Controls.Add(btnShowPdf)
        myShowPdf.Owner = Me
        btnShowPdf.Text = "Pdf wählen"
        btnShowPdf.top = 50
    End Sub
 
    Private Sub btnShowPdf_Click(ByVal sender As Object, _
        ByVal e As System.EventArgs) Handles btnShowPdf.Click
        With ofd
            .Filter = "Pdf-Files|*.pdf"
            .CheckFileExists = True
            If .ShowDialog = _
            Windows.Forms.DialogResult.Cancel Then Exit Sub
            myShowPdf.PdfFile = .FileName
            myShowPdf.Show()
            Me.Hide()
        End With
    End Sub
End Class
 
Public Class frmShowPdf
 
    Dim WithEvents btnNeueSuche As New Button
    Dim _pdfFile As String
 
    Public Property PdfFile() As String
        Get
            Return _pdfFile
        End Get
        Set(ByVal value As String)
            _pdfFile = value
        End Set
    End Property
 
    Private Sub frmShowPdf_Load(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles MyBase.Load
        Me.Controls.Add(btnNeueSuche)
        btnNeueSuche.Top = Me.Height - 60
        btnNeueSuche.Text = "Neue Suche"
    End Sub
 
    Private Sub frmShowPdf_Activated(ByVal sender As Object, _
        ByVal e As System.EventArgs) Handles Me.Activated
        Me.Text = _pdfFile
        'Hier pdffile anzeigen
    End Sub
 
    Private Sub btnNeueSuche_Click(ByVal sender As Object, _
    ByVal e As System.EventArgs) Handles btnNeueSuche.Click
        Me.Owner.Show()
        Me.Hide()
    End Sub
 
    Private Sub frmShowPdf_FormClosing(ByVal sender As Object, _
        ByVal e As System.Windows.Forms.FormClosingEventArgs) _
        Handles Me.FormClosing
        If e.CloseReason = CloseReason.UserClosing Then
            e.Cancel = True
        End If
    End Sub
End Class