I know there are providers out there doing the job really well but i would like to add to a site the ability:

1  for a reg user to upload a large file giving a period for the files to be kept.
2 the site requests the email address(es) of those who are invited/allowed to download the file
3 the site sends an email to the people who can then click link to allow the download to their computer
4 the site deletes the file within the time set by the user in step 1

I have not been able to find something to do the job just yet but figured there must be something out there?

and thanks lee for the informative and amusing email updates each month

I have not come across something which allows all of those elements, however it could be worth contacting the module developers who already have a document management module such as: http://www.bring2mind.net/ document exchange module.

Sometimes module developers will add extra features for a nominal fee which I have found to be a useful way of quickly getting features added to a module, so that could be worth considering.

Glad you find the site useful, thanks,