All official Dolibarr documentation is available online in Dolibarr wiki website. You will find users, developers and translators documentation but also information about Dolibarr project.
To go onto wiki web site, click http://wiki.dolibarr.org
You may also find non official documentation (nor written, nor validated by Dolibarr dev team), available as PDF files, onto Dolistore (the Dolibarr market place).
Try a seach on DoliStore.