rtf2rtf: 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/rtf2rtf - from package: linuxdoc-tools

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

Error in other languages:
rtf2rtf: bevel nie gevind nie
rtf2rtf: comandă negăsită
rtf2rtf: comando não encontrado
rtf2rtf: commande introuvable
rtf2rtf: command not found
rtf2rtf: käsku ei ole
rtf2rtf: không tìm thấy lệnh
rtf2rtf: komanda nerasta
rtf2rtf: Kommando nicht gefunden.
rtf2rtf: kommandot finns inte
rtf2rtf: komut yok
rtf2rtf: nie znaleziono polecenia
rtf2rtf: níor aimsíodh an t-ordú
rtf2rtf: no se encontró la orden
rtf2rtf: no s'ha trobat l'ordre
rtf2rtf: opdracht niet gevonden
rtf2rtf: parancs nem található
rtf2rtf: perintah tidak ditemukan
rtf2rtf: príkaz nenájdený
rtf2rtf: příkaz nenalezen
rtf2rtf: команда не найдена
rtf2rtf: командата не е открита
rtf2rtf: 命令找不到
rtf2rtf: コマンドが見つかりません