pdftotext: 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 CentOS possible default full paths are:

/usr/bin/pdftotext - from package: poppler-utils

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/pdftotext - from package: poppler-utils

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

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