asciidoctor: 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/asciidoctor - from package: rubygem-asciidoctor
/usr/lib/ruby/gems/1.8/gems/asciidoctor-0.1.3/bin/asciidoctor - from package: rubygem-asciidoctor

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

On Debian possible default full paths are:

/usr/bin/asciidoctor - from package: asciidoctor

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

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