pbmtocmuwm: 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/pbmtocmuwm - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/pbmtocmuwm - from package: netpbm

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

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