umax_pp: 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/umax_pp - from package: sane-utils

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

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