This is not a document, per se. The word "perdoname" (perdóname) is found scratched into the rock wall next to the corpse of the woman in the Mountain Pass tunnel. It's not known at this time who scratched this word into the wall. If it was the woman's husband, who was the author of the Farewell Map, it was written after the letter on the map was written, as he had not found his wife at that time.
It could have been written as a final act of the wife, in anguish of not having been able to survive to reunite with her husband.
It is possible that either of them wrote it in apology to the other for suggesting that they visit the island.
It is also possible that it was written by neither of them. It could have been written by an unknown third party, sympathetic to the young woman's death for reasons unknown.
The word translates from Spanish to "forgive me".
Russian: прости меня
German: vergib mir