changerefkeys: 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/changerefkeys - from package: libcam-pdf-perl

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

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