htdig-pdfparser: 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/htdig-pdfparser - from package: htdig

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

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