ppdc: 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/ppdc - from package: cups

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

On Debian possible default full paths are:

/usr/bin/ppdc - from package: cups-ppdc

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

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