ocamldoc: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/ocamldoc - from package: ocaml-ocamldoc

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/ocamldoc - from package: ocaml-nox

You may install the required package with command apt-get install {package}

Error in other languages:
ocamldoc: bevel nie gevind nie
ocamldoc: comandă negăsită
ocamldoc: comando não encontrado
ocamldoc: commande introuvable
ocamldoc: command not found
ocamldoc: käsku ei ole
ocamldoc: không tìm thấy lệnh
ocamldoc: komanda nerasta
ocamldoc: Kommando nicht gefunden.
ocamldoc: kommandot finns inte
ocamldoc: komut yok
ocamldoc: nie znaleziono polecenia
ocamldoc: níor aimsíodh an t-ordú
ocamldoc: no se encontró la orden
ocamldoc: no s'ha trobat l'ordre
ocamldoc: opdracht niet gevonden
ocamldoc: parancs nem található
ocamldoc: perintah tidak ditemukan
ocamldoc: príkaz nenájdený
ocamldoc: příkaz nenalezen
ocamldoc: команда не найдена
ocamldoc: командата не е открита
ocamldoc: 命令找不到
ocamldoc: コマンドが見つかりません