Is it permissible to recite Surat Al-Kahf twice on Friday, once in the morning and once in the evening, and is that considered an innovation (bid‘ah)?

There is no harm in frequently reciting Surat al-Kahf daily, due to what has been reported regarding the virtue of reciting it, namely that it is "a light from his station to Mecca" and that whoever recites ten verses from its end will not be afflicted by the Dajjal. There is no harm in reciting it in the morning and evening for those who do not believe that it is a Sunnah (definition).