pdftohtml: 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/pdftohtml - from package: poppler-utils

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

On Debian possible default full paths are:

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

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

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