Documents? I had the strong impression that there are no documents written in runes. A rune we only know by its occurrence in documents would be far more interesting for the existence of a document than it would be for its own sake!
Compare what the page about Anglo-Saxon runes says about the corpus:
> The Old English and Old Frisian Runic Inscriptions database project at the Catholic University of Eichstätt-Ingolstadt, Germany aims at collecting the genuine corpus of Old English inscriptions containing more than two runes in its paper edition, while the electronic edition aims at including both genuine and doubtful inscriptions down to single-rune inscriptions.
> The corpus of the paper edition encompasses about one hundred objects (including stone slabs, stone crosses, bones, rings, brooches, weapons, urns, a writing tablet, tweezers, a sun-dial,[clarification needed] comb, bracteates, caskets, a font, dishes, and graffiti). The database includes, in addition, 16 inscriptions containing a single rune, several runic coins, and 8 cases of dubious runic characters (runelike signs, possible Latin characters, weathered characters). Comprising fewer than 200 inscriptions, the corpus is slightly larger than that of Continental Elder Futhark (about 80 inscriptions, c. 400–700), but slightly smaller than that of the Scandinavian Elder Futhark (about 260 inscriptions, c. 200–800).
So across every runic system we know, we have under 600 texts, all of those texts are short inscriptions, and even to reach that number of samples we need to include texts that we aren't even sure contain any runes.