Changing extentions names of files in folder that never had an ext in the first place?

ok love this place! I found this online... it works! but my files have no extensions in the very first place so I tried * and *. and i guess the vba gurus know of a magical symbol to use

If you know! lemme know thanks..

Sub changeExt()

strDir = "C:\myFolder\" 'mention your files folder path here

With CreateObject("wscript.shell")

   .currentdirectory = strDir

   .Run "%comspec% /c ren *.xlsx *.xls", 0, True

''''''''     .Run "%comspec% /c ren ???? HERE HAS NO EXTENSION WHAT TO DO ????? *.pdf", 0, True  ???? so imagine a folder with files with no extensions and I need .pdf on all of them

End With

End Sub

Thanks guys this is by far the most reliable site on the internet for what now... the last 20 years!