update-pdf-help: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/update-pdf-help - from package: gosa-dev

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