readpdf: 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/readpdf - from package: libcam-pdf-perl

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

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