DOCman already comes in 47 languages, you can easily add your own language, or, if you find that a language file is incomplete you can update anything that's missing, by joining our army of translators.
This process ensures that your translation will be included in the next maintenance release and all future versions of DOCman.
Just follow these steps:
Sign up for a Transifex account: https://www.transifex.com/signup/, if you don't already have one.
Once you're logged in, go directly to the Joomlatools projects page https://explore.transifex.com/joomlatools/.
Select DOCman from the list of available translation projects and click the Join this project button in the sidebar.
Select the language that you'd like to add a translation for and join the project.
Once your request has been granted you'll be able to add a translation for any untranslated text strings.