pstopdf: 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/pstopdf - from package: texlive-context

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

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