rpdfcrop: 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/rpdfcrop - from package: texlive-extra-utils

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

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