If you want to use in an already existing Project the keyword-substitution in Subversin as described here: Subversion Keywords (Revision,Author,URL,Date,ID) you have to set the properties to substitute these keywords for all existing files, too.
This can be done e.g. in Tortoise SVN in the contextmenu-properties-new
Just check in the needed Keywords an click OK.
You can the properties for every single file or recursively for an directory:
After setting this properties, alle the files have to be checked in!
More information can be found here.