xmlto: 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/xmlto - from package: xmlto

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

On Debian possible default full paths are:

/usr/bin/xmlto - from package: xmlto

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

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