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)