Scusami pensavo fosse sufficiente la spigazione, dato che pensavo fosse un problema circoscritto all'oggetto pdf chiuso nel modo scorretto.
Ecco il codice.
codice:
Public Class ListProfile
    Dim db As New Database

    Private Sub ListProfile_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        AggiornaProfili()
    End Sub

    Private Sub ListProfile_Activated(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Activated
        ModelView.Focus()
        ModelView.Items(0).Selected = True
        'CaricaDatiFigurini()
    End Sub

    Private Sub CaricaDatiFigurini()

        If ModelView.SelectedItems.Count <> 0 Then
            Dim FilePdf As String
            PictureBoxFigurini.Image = Image.FromFile(System.Environment.CurrentDirectory + "\images\figurini\" + ModelView.SelectedItems(0).SubItems(0).Text + ".jpg")
            FilePdf = System.Environment.CurrentDirectory + "\doc\doc_tecnica\" + GeneralModel.language + "\" + ModelView.SelectedItems(0).SubItems(0).Text + ".pdf"
            If System.IO.File.Exists(FilePdf) Then
                TecDocPDF.src = FilePdf
            Else
                If GeneralModel.language = "ITA" Then
                    MessageBox.Show("Il file richiesto non è valido." & vbCrLf & "Contattare il supporto tecnico per correggere il problema", "Errore!")
                ElseIf GeneralModel.language = "ENG" Then
                    MessageBox.Show("The requested file is not valid." & vbCrLf & "Contact technical support", "Error!")
                End If
            End If

        End If
    End Sub
    Private Sub AggiornaProfili() Handles NameSearch.KeyUp
        db.Connetti()

        Dim Sql As String

        Dim dt As New DataTable
        Dim ds As New DataSet
        ds.Tables.Add(dt)

        Sql = "SELECT * FROM modelli WHERE modello_nome LIKE '%" & NameSearch.Text & "%'"

        Dim da As New OleDb.OleDbDataAdapter(Sql, db.istance)
        da.Fill(dt)

        ModelView.Items.Clear()
        For Each myRows In dt.Rows
            Sql = "SELECT COUNT(*) FROM Allegati WHERE modello_id = " & CInt(myRows.Item("modello_id"))
            Dim command As New OleDb.OleDbCommand(Sql, db.istance)
            Dim reader As OleDb.OleDbDataReader = command.ExecuteReader()
            reader.Read()
            If reader(0).ToString() > 0 Then
                ModelView.Items.Add(myRows.Item("modello_id"), 0)
            Else
                ModelView.Items.Add(myRows.Item("modello_id"), 1)
            End If

            ModelView.Items(ModelView.Items.Count - 1).SubItems.Add(myRows.Item("modello_nome"))
            ModelView.Items(ModelView.Items.Count - 1).SubItems.Add(myRows.Item("modello_anno"))
        Next

        db.Disconnetti()
    End Sub

    Private Sub ResetDescButton(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ImgClose.MouseLeave, BeforeForm.MouseLeave
        DescButton.Text = " "
    End Sub

    Private Sub ImgClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ImgClose.Click
        TecDocPDF.Dispose()
        Application.Exit()
    End Sub

    Private Sub ImgClose_MouseHover(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ImgClose.MouseHover
        If GeneralModel.language = "ITA" Then
            DescButton.Text = "Chiudi Programma"
        ElseIf GeneralModel.language = "ENG" Then
            DescButton.Text = "Exit Program"
        End If
    End Sub

    Private Sub BeforeForm_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BeforeForm.Click
        TecDocPDF.Dispose()
        Me.Close()
        MainMenu.Show()
    End Sub

    Private Sub BeforeForm_MouseHover(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BeforeForm.MouseHover
        If GeneralModel.language = "ITA" Then
            DescButton.Text = "Torna all' indice precedente"
        ElseIf GeneralModel.language = "ENG" Then
            DescButton.Text = "GoTo previous index"
        End If
    End Sub

    Private Sub ModelView_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ModelView.SelectedIndexChanged
        CaricaDatiFigurini()
        ModelView.Focus()
    End Sub

    Private Sub TecDocPDF_OnError(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TecDocPDF.OnError

    End Sub

    Private Sub Confirm_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Confirm.Click
        'Apri Lista Documentazione Tecnica

        DocTec.idmodel = ModelView.SelectedItems(0).SubItems(0).Text
        DocTec.NameModel = ModelView.SelectedItems(0).SubItems(1).Text
        Me.Close()
        DocTec.Show()

        'Dim IdModel As Integer
        'IdModel = CInt(ModelView.SelectedItems(0).SubItems(0).Text)

        'Dim Sql

        'ModelView.Items.Clear()
        'ModelView.Columns.Clear()

        'ModelView.Columns.Add("Tipologia")
        'ModelView.Columns.Add("File")
        'ModelView.Columns.Add("Language")

        'db.Connetti()

        'Sql = "SELECT Allegati.allegato_file, Allegati.allegato_lang, Allegati_Tipo.allegatotipo_desc FROM Allegati "
        'Sql = Sql & "INNER JOIN Allegati_Tipo ON Allegati.allegatotipo_id = Allegati_Tipo.allegatotipo_id "
        'Sql = Sql & "WHERE modello_id = " & IdModel
        'Dim command As New OleDb.OleDbCommand(Sql, db.istance)
        'Dim reader As OleDb.OleDbDataReader = command.ExecuteReader()
        'While reader.Read()
        '    ModelView.Items.Add(reader("allegatotipo_desc").ToString)
        '    ModelView.Items(ModelView.Items.Count - 1).SubItems.Add(reader("allegato_file").ToString)
        '    ModelView.Items(ModelView.Items.Count - 1).SubItems.Add(reader("allegato_lang").ToString)
        'End While

        'db.Disconnetti()
    End Sub
End Class