pbmtomgr: 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/pbmtomgr - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/pbmtomgr - from package: netpbm

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

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