djview4: 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 Debian possible default full paths are:

/usr/bin/djview4 - from package: djview4

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

Error in other languages:
djview4: bevel nie gevind nie
djview4: comandă negăsită
djview4: comando não encontrado
djview4: commande introuvable
djview4: command not found
djview4: käsku ei ole
djview4: không tìm thấy lệnh
djview4: komanda nerasta
djview4: Kommando nicht gefunden.
djview4: kommandot finns inte
djview4: komut yok
djview4: nie znaleziono polecenia
djview4: níor aimsíodh an t-ordú
djview4: no se encontró la orden
djview4: no s'ha trobat l'ordre
djview4: opdracht niet gevonden
djview4: parancs nem található
djview4: perintah tidak ditemukan
djview4: príkaz nenájdený
djview4: příkaz nenalezen
djview4: команда не найдена
djview4: командата не е открита
djview4: 命令找不到
djview4: コマンドが見つかりません