A cleaner version is attainable since the range  is explicitly called by the
worksheet index. With the worksheet references, you don't have to 'change' to
each worksheet so you are saving process cycles from the screen refreshes that
would have taken place. You could also set ScreenUpdating to false & then back
to True; does the same thing! Anyway see if this version makes sense:

Sub SetPrintAreaAllSheets3()

Dim vPrintrange As String

For SheetIndex = 1 To ActiveWorkbook.Sheets.Count

vPrintrange = "A1:" & Sheets(SheetIndex).Cells.SpecialCells(xlLastCell).Address

Sheets(SheetIndex).PageSetup.PrintArea = vPrintrange 'Set the print  range

Next SheetIndex

End Sub