gtkdocize: 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/gtkdocize - from package: gtk-doc

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

On Debian possible default full paths are:

/usr/bin/gtkdocize - from package: gtk-doc-tools

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

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