Insert a text content control where you want the number to be displayed and title it Startnumber then:
Code:
Sub PrintJobs()
Dim i As Long, startnum As Long, lastnum As Long
startnum = InputBox("Enter the first job number to be printed", "Print Job Number", 1)
lastnum = InputBox("Enter the last job number to be printed", "Print Job Number", 1)
For i = startnum To lastnum
ActiveDocument.SelectContentControlsByTitle("Serialnumber").Item(1).Range.Text = i
ActiveDocument.PrintOut
Next
End Sub
See also
Auto number documents