This whitepaper is called Off-By-One Exploitation Tutorial. The off by one vulnerability in general means that if an attacker supplied input with certain length if the program has an incorrect length condition the program will write one byte outside the bounds of the space allocated to hold this input causing one of two scenarios depending on the input.
You can download it from the following link: https://packetstormsecurity.com/files/download/123361/offbyone-tutorial.pdf
Source: https://packetstormsecurity.com/files/123361/Off-By-One-Exploitation-Tutorial.html