pbmtolps: 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/pbmtolps - from package: netpbm-progs

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

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