How to convert PPT to PDF and Html to pdf

Public Function CovertPPTXDocumenttoPDF(PowerPointFilePath As [String]) As PDFDocument
   Dim doc As New PPTXDocument(PowerPointFilePath)

   Dim imgSource As New List(Of REImage)()

   For i As Integer = 0 To doc.GetPageCount() - 1
      Dim page As PPTXPage = DirectCast(doc.GetPage(i), PPTXPage)

      Dim temp As REImage = DirectCast(page.ToImage(), REImage)
      If temp IsNot Nothing Then
         imgSource.Add(temp)
      End If
   Next
   ' create PDFDocument with image source
   Return New PDFDocument(imgSource)
End Function