This is the 11469th most frequent Russian word.
документального
"Documentary" or "related to documents."
In this sentence, 'документального' is used as an adjective describing the noun 'кино', meaning 'documentary.'
Я люблю смотреть документального кино.
I love watching documentary films.
Here, 'документального' describes 'характера,' indicating a characteristic related to documentary evidence.
Для написания статьи о истории мне потребуется материал документального характера.
To write an article about history, I will need materials of a documentary nature.
In this context, 'документального' is used to qualify 'происхождения,' referring to the documentary nature of the items' origin.