apertium-desrtf: 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 Debian possible default full paths are:

/usr/bin/apertium-desrtf - from package: apertium

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

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