pbmtoatk: 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/pbmtoatk - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/pbmtoatk - from package: netpbm

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

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