Using Add ins for files downloadable through web
 

I have couple of files accessible/downloadable through web. I am planning to
use Add-ins (some common set of code/functions, forms to be attached to all
the files).

Firstly, am i thinking the right approach/logic?

Secondly, Can i keep the add-in on the server and attach it to all the files
and use the form and code in the add-in's. And is there a way that when one
downloads a file to it's own PC and gets d'connected to the internet the
add'in utilities can still be used.

Suggestions will be highly appreciated.
--
Ajit