The Find/replace code recorded by the macro recorder is actually one of the more efficient recorder products, but you've omitted the important first two lines! For what you've indicated, you could use either of:
Sub Demo1()
Application.ScreenUpdating = False
With ActiveDocument.Range.Find
.ClearFormatting
.Replacement.ClearFormatting
.Forward = True
.MatchCase = False
.MatchWholeWord = True
.MatchWildcards = False
.Wrap = wdFindContinue
.Replacement.Text = "Employee ID"
.Text = "ID"
.Execute Replace:=wdReplaceAll
.Text = "eID"
.Execute Replace:=wdReplaceAll
.Text = "empID"
.Execute Replace:=wdReplaceAll
.Text = "employeeID"
.Execute Replace:=wdReplaceAll
End With
Application.ScreenUpdating = True
End Sub
or
Sub Demo2()
Application.ScreenUpdating = False
Dim StrFnd(), i As Long
StrFnd() = Array("ID", "eID", "empID", "employeeID")
With ActiveDocument.Range.Find
.ClearFormatting
.Replacement.ClearFormatting
.Forward = True
.MatchCase = False
.MatchWholeWord = True
.MatchWildcards = False
.Wrap = wdFindContinue
.Replacement.Text = "Employee ID"
For i = 0 To UBound(StrFnd)
.Text = StrFnd(i)
.Execute Replace:=wdReplaceAll
Next
End With
Application.ScreenUpdating = True
End Sub