Verily, this (the Quran) is no less than a Reminder to (all) the 'Alamin (mankind and jinns). (Qur'an 81:27)
So, for sure, it is a guidance for humans, and it is for Jinn too.
And when we(Jinn) heard the guidance, we believed in it. And whoever believes in his Lord will not fear deprivation or burden. (Qur'an 72:13)
And (remember) when We sent towards you (Muhammad SAW) Nafran (three to ten persons) of the jinns, (quietly) listening to the Quran, when they stood in the presence thereof, they said: "Listen in silence!" And when it was finished, they returned to their people, as warners. (Qur'an 46:29)
(It has been revealed to me that) When the slave of Allah (Muhammad SAW) stood up invoking (his Lord Allah) in prayer to Him they (the jinns) just made round him a dense crowd as if sticking one over the other (in order to listen to the Prophet's recitation) (Qur'an 72:19)
If so how is it guaranteed that they come to know of it?
We don't know. It is a matter of the unseen. But, to guess, as the above two verses say, when someone recites Qur'an, the jinn might listen to the reciter. We're unsure because, the verse describes about an event which happened, but does not say that it will always happen that way. So, beyond our scope.
And what about the Angels?
Indeed, We have made it an Arabic Qur'an that you might understand. And indeed it is, in the Mother of the Book with Us, exalted and full of wisdom. (Qur'an 43:3-4)
Again these are the verses which just give a clue, but are not clear. The same Qur'an which we have might be of guidance to the angels too(i.e. they may consider the verses useful for them out of that Qur'an) or may be the rules pertaining to them are inscribed in the "Mother of The Book" which we have no knowledge of.
May the creator guide us all.