You cannot use non-contiguous ranges with ExportAsFixedFormat you would need to use the PDF printer driver to achieve that. e.g.
Code:
Sub PrintAsPDF()
'Graham Mayor - https://www.gmayor.com - Last updated - 14 Aug 2021
Dim sPrinter As String
Dim sRange As String
On Error GoTo lbl_Exit
sPrinter = Application.ActivePrinter
ActivePrinter = "Microsoft Print to PDF"
sRange = InputBox("Enter the range of pages to be printed eg 1" & vbCr & _
"or 1-3" & vbCr & _
"or 1-3,6", "Print Pages")
If sRange = "" Then
MsgBox "No pages selected!", vbCritical, "Print Pages"
GoTo lbl_Exit
End If
Application.PrintOut FileName:="", _
Range:=wdPrintRangeOfPages, _
Item:=wdPrintDocumentWithMarkup, _
copies:=1, _
Pages:=sRange, _
PageType:=wdPrintAllPages, _
collate:=True, _
Background:=False, _
PrintToFile:=False, _
PrintZoomColumn:=0, _
PrintZoomRow:=0, _
PrintZoomPaperWidth:=0, _
PrintZoomPaperHeight:=0
lbl_Exit:
Application.ActivePrinter = sPrinter
Exit Sub
End Sub