We have requirement for on demand publishing of office document from a document library, what are the steps to configure word automation service in SharePoint 2013 to archive the same functionality also let me know what coding is required....any sample code would be great.

Technically this reference is for 2010, but it works the same way in 2013.

http://msdn.microsoft.com/en-us/library/office/ff181518(v=office.14).aspx

I have a project here you can leverage (or modify the code if it doesn't meet your needs) - http://was.codeplex.com.