gscan2pdf: 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/gscan2pdf - from package: gscan2pdf

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

Error in other languages:
gscan2pdf: bevel nie gevind nie
gscan2pdf: comandă negăsită
gscan2pdf: comando não encontrado
gscan2pdf: commande introuvable
gscan2pdf: command not found
gscan2pdf: käsku ei ole
gscan2pdf: không tìm thấy lệnh
gscan2pdf: komanda nerasta
gscan2pdf: Kommando nicht gefunden.
gscan2pdf: kommandot finns inte
gscan2pdf: komut yok
gscan2pdf: nie znaleziono polecenia
gscan2pdf: níor aimsíodh an t-ordú
gscan2pdf: no se encontró la orden
gscan2pdf: no s'ha trobat l'ordre
gscan2pdf: opdracht niet gevonden
gscan2pdf: parancs nem található
gscan2pdf: perintah tidak ditemukan
gscan2pdf: príkaz nenájdený
gscan2pdf: příkaz nenalezen
gscan2pdf: команда не найдена
gscan2pdf: командата не е открита
gscan2pdf: 命令找不到
gscan2pdf: コマンドが見つかりません