I may be wrong but doesn't Inno setup automatically pick up all the profiles on the target PC and prompt the user to select which profiles to add paths to ?
(you can also specify a completely new profile to use or copy from an existing one)
beware though, if you are adding lines to the Acaddoc.lsp, if one doesn't exist, Inno creates one in the first_support_path it finds ~ which is (one of)the one(s) you just added.