texdoc: 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/texdoc - from package: texlive-base

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

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