I've installed r12.1 on Linux, now there is a requirement to add french to this installation. Is this doable ? .. Any pointers will be of great help
It is doable.
Please see these docs and old threads for similar discussion.
Oracle Applications NLS Release Notes, Release 12.1 [ID 788053.1]
How to resolve NLS translation issues in an Ebusiness Suite 11i and R12 environment [ID 394112.1]
Requesting Translation Synchronization Patches [ID 252422.1] Re: French language is not coming in GL and AP responsibility