sldtoppm: 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/sldtoppm - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/sldtoppm - from package: netpbm

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

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