Combine Single PDF

Dear All , The below code is for export as different PDF Files , But how to Combilne all files as Single PDF File

Option Explicit

Sub SaveAsButton()
Application.ScreenUpdating = False

' for PDF file save
Sheet2.Range("$A$1:$E$35").ExportAsFixedFormat xlTypePDF, Filename:= _
"D:\" & Sheet2.Range("B17").Value, OpenAfterPublish:=False
Application.ScreenUpdating = True

End Sub

Sub All()
Application.ScreenUpdating = False
Dim I As Long
I = 2

Do Until Sheet5.Cells(I, 1).Value = Empty
    Sheet2.Range("B17").Value = Sheet5.Cells(I, 1).Value
    Call SaveAsButton
I = I + 1
Loop
Application.ScreenUpdating = True

End Sub