CB Package Manager isn't capable of modifying the files. You could add the username or user id to the filename, but not in the file itself. The URL I suppose could be whatever you wanted with a custom URL rewriting rule I guess, but packages in CB Package Builder are not user specific. Meaning you wouldn't be making 1 package for every user. There would simply be 1 package. Doesn't sound like it'd fit your usage. You'd probably need to use CB Auto Actions and a Code action then on the output set the appropriate headers to serve a download.