Launch pdf and close on delete window event

[Gribouillis]

Not a windows user here but instead of opening the pdf with os.startfile(), which creates another process out of the reach of your program, you could launch directly a specific pdf viewer with the subprocess module. For example supposing you open pdf files with Acrobat Reader, it could be

viewer = shutil.which('AcroRd32')
proc = Popen([viewer, filename])
processes.append(proc)