pamtopam: command not found

Have You tried accessing the binary with the full path?

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/pamtopam - from package: netpbm-progs

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