Compile Error while checking if worksheet exists....

Hello,

I have a slight problem. Whenever I run the code below I get an error Message: "Compile Error ByRef argument type mismatch" And the Sheet9 (marked in red here) is marked yellow in the debugging mode.

Obviously my code there is not valid but how to modify it so that it will work?

Just in case it is not Clear what I want to achieve is simply that I want the Macro to check IF there is a Sheet9 (IF it exists in the WorkBook) and if YES then add it as a PDF attachement as well. If it does NOT exists then go on With the macro.

Sub SaveAsPDF(ws As Worksheet, FullPath As String)

    FullPath = ThisWorkbook.Path & "\" & ws.Name & ".PDF"
    
    ws.ExportAsFixedFormat _
      Type:=xlTypePDF, _
      Filename:=FullPath
      
End Sub

Sub Mail_Workbook_1()
    Dim OutApp As Object
    Dim OutMail As Object
    Dim Signature As String

    Dim FullPath As String
    
    Set OutApp = CreateObject("Outlook.Application")
    Set OutMail = OutApp.CreateItem(0)
    
    With OutMail
    .Display
    End With
        Signature = OutMail.htmlbody
    
    On Error Resume Next
    With OutMail
        .To = Range("D10").Value
        .CC = ""
        .BCC = ""
        .Subject = "Papirer Bestilling"
        .htmlbody = "<BR>test" & Signature
            
      
        If Sheet3.Visible = xlSheetVisible Then
        SaveAsPDF Sheet3, FullPath
        .Attachments.Add FullPath
        End If
        
        If Sheet4.Visible = xlSheetVisible Then
        SaveAsPDF Sheet4, FullPath
        .Attachments.Add FullPath
        End If
        
        If Sheet6.Visible = xlSheetVisible Then
        SaveAsPDF Sheet6, FullPath
        .Attachments.Add FullPath
        End If
        
        If Sheet7.Visible = xlSheetVisible Then
        SaveAsPDF Sheet7, FullPath
        .Attachments.Add FullPath
        End If
        
        If Sheet8.Visible = xlSheetVisible Then
        SaveAsPDF Sheet8, FullPath
        .Attachments.Add FullPath
        End If
        
        If WorksheetExists = Sheets(Sheet9) Then
        SaveAsPDF Sheet9, FullPath
        .Attachments.Add FullPath
        End If

        
        .Display
    End With
    On Error GoTo 0

    Set OutMail = Nothing
    Set OutApp = Nothing
End Sub