Using Select Case allows you to be much more succinct with your code by grouping values. There is no value in the goto statement since the code would go there next anyway
Code:
Sub PrintLetterhead()
Dim defprinter As String
defprinter = UCase(Mid(ActivePrinter, 1, 20))
Select Case defprinter
Case "\\GS-DC2\MFP1", "\\GS-DC2\MFP2", "\\GS-DC2\MFP3", "\\GS-DC2\MFP4", "BOOKKEEPING XEROX WORKCENTRE PRO 5335"
With ActiveDocument.PageSetup
.FirstPageTray = 260
.OtherPagesTray = 259
End With
Case "\\GS-DC2\MFP5", "\\GS-DC2\MFP6"
With ActiveDocument.PageSetup
.FirstPageTray = wdPrinterMiddleBin
.OtherPagesTray = wdPrinterLowerBin
End With
Case Else
With ActiveDocument.PageSetup
.FirstPageTray = 258
.OtherPagesTray = 259
End With
End Select