pdfinfo: 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/pdfinfo - from package: poppler-utils

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

On Debian possible default full paths are:

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

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

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