psidtopgm: 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/psidtopgm - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/psidtopgm - from package: netpbm

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

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