pkenhance: 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/pkenhance - from package: pktools

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

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