pn53x-sam: 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
/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/pn53x-sam - from package: libnfc-pn53x-examples

You may install the required package with command apt-get install {package}
Error in other languages:
pn53x-sam: bevel nie gevind nie
pn53x-sam: comandă negăsită
pn53x-sam: comando não encontrado
pn53x-sam: commande introuvable
pn53x-sam: command not found
pn53x-sam: käsku ei ole
pn53x-sam: không tìm thấy lệnh
pn53x-sam: komanda nerasta
pn53x-sam: Kommando nicht gefunden.
pn53x-sam: kommandot finns inte
pn53x-sam: komut yok
pn53x-sam: nie znaleziono polecenia
pn53x-sam: níor aimsíodh an t-ordú
pn53x-sam: no se encontró la orden
pn53x-sam: no s'ha trobat l'ordre
pn53x-sam: opdracht niet gevonden
pn53x-sam: parancs nem található
pn53x-sam: perintah tidak ditemukan
pn53x-sam: príkaz nenájdený
pn53x-sam: příkaz nenalezen
pn53x-sam: команда не найдена
pn53x-sam: командата не е открита
pn53x-sam: 命令找不到
pn53x-sam: コマンドが見つかりません