sisu-pdf-portrait: 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/sisu-pdf-portrait - from package: sisu-pdf

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

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