pbmclean: 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/pbmclean - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/pbmclean - from package: netpbm

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

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