cpaldjvu: 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/cpaldjvu - from package: djvulibre

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

On Debian possible default full paths are:

/usr/bin/cpaldjvu - from package: djvulibre-bin

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

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