ppmdcfont: 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/ppmdcfont - from package: netpbm-progs

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

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