Hi,
When Odoo launch the download action of a report it will check if close_on_report_download action attribute is set to true, if so it will return action of type ir.actions.act_window_close which will close the wizard.

@api.multi
def print_pdf(self):
 action = self.env.ref('customer_products.pdf_products').report_action(self)
 action.update({'close_on_report_download': True})
return action

Regards