import re
content = """
widgetEvCall('handlers.onMenuClicked', event, this, 'http://w...content-available-to-author-only...n.be/medias/documents/20181002_carte_octobre-novembre_2018_FR.pdf')
"""
link = ''
m = re.search(r"this,\s*'([^']*)'", content)
if m:
link = m.group(1)
print(link)
aW1wb3J0IHJlCgpjb250ZW50ID0gIiIiCndpZGdldEV2Q2FsbCgnaGFuZGxlcnMub25NZW51Q2xpY2tlZCcsIGV2ZW50LCB0aGlzLCAnaHR0cDovL3cuLi5jb250ZW50LWF2YWlsYWJsZS10by1hdXRob3Itb25seS4uLm4uYmUvbWVkaWFzL2RvY3VtZW50cy8yMDE4MTAwMl9jYXJ0ZV9vY3RvYnJlLW5vdmVtYnJlXzIwMThfRlIucGRmJykKIiIiCmxpbmsgPSAnJwptID0gcmUuc2VhcmNoKHIidGhpcyxccyonKFteJ10qKSciLCBjb250ZW50KQppZiBtOgoJbGluayA9IG0uZ3JvdXAoMSkKCQpwcmludChsaW5rKQ==