Sub Demo()
With Selection
  .Paste
  With .Find
    .ClearFormatting
    .Replacement.ClearFormatting
    .Text = "https://doi.org/"
    .Replacement.Text = "doi:^c"
    .Forward = True
    .Wrap = wdFindContinue
    .Format = False
    .MatchCase = False
    .MatchWholeWord = False
    .MatchWildcards = False
    .MatchSoundsLike = False
    .MatchAllWordForms = False
    .Execute Replace:=wdReplaceOne
  End With
  If .Find.Found = True Then
    .Start = .Start + 4
    .Hyperlinks.Add Anchor:=.Range, Address:="https://" & .Text, TextToDisplay:=.Text
  End If
End With
End Sub