import re
strings = [
r"C:\temp\John Smith Junior\file.pdf",
r"C:\temp\John Smith Junior\John Smith Junior\file.pdf",
r"C:\temp\John Smith Junior file.pdf"
]
for s in strings:
m = re.match(r".*?\bJunior\b(\\)?(?(1)|.*)", s)
if m:
print(m.group())
aW1wb3J0IHJlCgpzdHJpbmdzID0gWwoJciJDOlx0ZW1wXEpvaG4gU21pdGggSnVuaW9yXGZpbGUucGRmIiwKCXIiQzpcdGVtcFxKb2huIFNtaXRoIEp1bmlvclxKb2huIFNtaXRoIEp1bmlvclxmaWxlLnBkZiIsCglyIkM6XHRlbXBcSm9obiBTbWl0aCBKdW5pb3IgZmlsZS5wZGYiCl0KCmZvciBzIGluIHN0cmluZ3M6CgltID0gcmUubWF0Y2gociIuKj9cYkp1bmlvclxiKFxcKT8oPygxKXwuKikiLCBzKQoJaWYgbToKCQlwcmludChtLmdyb3VwKCkp