pamtotiff: 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

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/pamtotiff - from package: netpbm-progs

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