chm2pdf: 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/chm2pdf - from package: chm2pdf

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

On Debian possible default full paths are:

/usr/bin/chm2pdf - from package: chm2pdf

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

Error in other languages:
chm2pdf: bevel nie gevind nie
chm2pdf: comandă negăsită
chm2pdf: comando não encontrado
chm2pdf: commande introuvable
chm2pdf: command not found
chm2pdf: käsku ei ole
chm2pdf: không tìm thấy lệnh
chm2pdf: komanda nerasta
chm2pdf: Kommando nicht gefunden.
chm2pdf: kommandot finns inte
chm2pdf: komut yok
chm2pdf: nie znaleziono polecenia
chm2pdf: níor aimsíodh an t-ordú
chm2pdf: no se encontró la orden
chm2pdf: no s'ha trobat l'ordre
chm2pdf: opdracht niet gevonden
chm2pdf: parancs nem található
chm2pdf: perintah tidak ditemukan
chm2pdf: príkaz nenájdený
chm2pdf: příkaz nenalezen
chm2pdf: команда не найдена
chm2pdf: командата не е открита
chm2pdf: 命令找不到
chm2pdf: コマンドが見つかりません