visitors downloading docs

My new blog use is not quite typical. Looking for experience and/or magic app (aren’t we all). We want to post architectural plans and specifications for download by consultants and contractors. when we issues revisions, they feed to everyone interested in that particular project. comments on files need to come straight back to us rather than post for all to see (i.e. reporting of an error in a doc) *.dwg files are available for consultants, *.pdf files for contractors, and specs in ms word for everyone. Want users to be able to dl .zip of the whole project or browse large thumbs of plans and pick and choose individual sheets which apply to them. In essence, the whole blog is about downloading project docs and receiving notices when revisions occur. we’ve done it as an html page of the main website but it’s cumbersome and simply “right click file name to dl” kind of crude. experience and suggestions are greatly appreciated!