pbmtoln03: 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/pbmtoln03 - from package: netpbm-progs

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

Error in other languages:
pbmtoln03: bevel nie gevind nie
pbmtoln03: comandă negăsită
pbmtoln03: comando não encontrado
pbmtoln03: commande introuvable
pbmtoln03: command not found
pbmtoln03: käsku ei ole
pbmtoln03: không tìm thấy lệnh
pbmtoln03: komanda nerasta
pbmtoln03: Kommando nicht gefunden.
pbmtoln03: kommandot finns inte
pbmtoln03: komut yok
pbmtoln03: nie znaleziono polecenia
pbmtoln03: níor aimsíodh an t-ordú
pbmtoln03: no se encontró la orden
pbmtoln03: no s'ha trobat l'ordre
pbmtoln03: opdracht niet gevonden
pbmtoln03: parancs nem található
pbmtoln03: perintah tidak ditemukan
pbmtoln03: príkaz nenájdený
pbmtoln03: příkaz nenalezen
pbmtoln03: команда не найдена
pbmtoln03: командата не е открита
pbmtoln03: 命令找不到
pbmtoln03: コマンドが見つかりません