Probably, because it won't compile.
Your two strings aren't delimited properly:
Pdf_file="""P:\VB Entwicklung\_Meine Projekte\ARRE\InBearbeitung\PM 20181011 2519.62 bkk9.pdf"""
Fdf_file="""P:\VB Entwicklung\_Meine Projekte\ARRE\InBearbeitung\formular.fdf"""
Should fix that.