didjvu: 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/didjvu - from package: didjvu

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

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