pbmtoescp2: 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/pbmtoescp2 - from package: netpbm-progs

You may install the required package with command yum install {package}
Error in other languages:
pbmtoescp2: bevel nie gevind nie
pbmtoescp2: comandă negăsită
pbmtoescp2: comando não encontrado
pbmtoescp2: commande introuvable
pbmtoescp2: command not found
pbmtoescp2: käsku ei ole
pbmtoescp2: không tìm thấy lệnh
pbmtoescp2: komanda nerasta
pbmtoescp2: Kommando nicht gefunden.
pbmtoescp2: kommandot finns inte
pbmtoescp2: komut yok
pbmtoescp2: nie znaleziono polecenia
pbmtoescp2: níor aimsíodh an t-ordú
pbmtoescp2: no se encontró la orden
pbmtoescp2: no s'ha trobat l'ordre
pbmtoescp2: opdracht niet gevonden
pbmtoescp2: parancs nem található
pbmtoescp2: perintah tidak ditemukan
pbmtoescp2: príkaz nenájdený
pbmtoescp2: příkaz nenalezen
pbmtoescp2: команда не найдена
pbmtoescp2: командата не е открита
pbmtoescp2: 命令找不到
pbmtoescp2: コマンドが見つかりません