You have to ask the permits at least 3 days before you go and you have to collect them in person. Normally in there HQ in Las Palmas, bur Arinaga is also possible.
There you receive the permits in 2 copies which you have to sign. Because they give both signed copies with you, I can't understand why they can't mail them too ...
Hopefullu this helps. Sorry it's in English, but my German is even worse :)
Die große Gran Canaria Tour - Von Süden nach NordenDetails