Below is the whole sub. You can use it in ArcMap VBA. I only a little C#. Maybe someone like Kirk can help out.
Dim pMxApp As IMxApplication
Dim pMxdoc As IMxDocument
Dim pactiveview As IActiveView
Dim pPageLayout As IPageLayout
Dim pExporter As IExporter
Dim pPrinter As IPrinter
Dim pRECT As tagRECT
Dim hDc As OLE_HANDLE
Dim pDriverBounds As IEnvelope
Dim pVisibleBounds As IEnvelope
Dim pPixelBounds As IEnvelope
Dim ipPixelBounds As IEnvelope
Dim width As Double
Dim height As Double
Dim FilePath As String
FilePath = "C:\"
Set pMxApp = Application
Set pMxdoc = ThisDocument
Set pactiveview = pMxdoc.ActiveView
Set pPageLayout = pMxdoc.PageLayout
Set pExporter = New PDFExporter
Set pPrinter = pMxApp.Printer
Set pVisibleBounds = New Envelope
Set pVisibleBounds = Nothing 'set to nothing unless clip to graphic extent is checked
Set pPixelBounds = New Envelope
pExporter.ExportFileName = FilePath & sFileName & ".pdf"
pExporter.Resolution = 300
pPrinter.QueryPaperSize width, height
pRECT.Left = 0
pRECT.Top = 0
pRECT.Right = width * pExporter.Resolution
pRECT.bottom = height * pExporter.Resolution
pPixelBounds.PutCoords pRECT.Left, pRECT.Top, pRECT.Right, pRECT.bottom
pExporter.PixelBounds = pPixelBounds
Dim pFME As IFontMapEnvironment
Set pFME = pExporter 'QI
Dim pFMC As IFontMapCollection
Set pFMC = pFME.FontMapCollection
Dim pFont As IFontMap2
Set pFont = New FontMap
'Arial is the TrueType font whereas Courier is the mapped font
pFont.SetMapping "Arial", "Arial"
pFMC.Add pFont
Set pFont = New FontMap
pFont.SetMapping "Arial Bold", "Helvetica-Bold"
pFMC.Add pFont
hDc = pExporter.StartExporting
pMxdoc.ActiveView.Output hDc, pExporter.Resolution, pRECT, pVisibleBounds, Nothing
pExporter.FinishExporting
