I'd like to create a site that allows users to create a post and upload documents attached to it in a variety of formats, probably mostly DOC, TXT, XLS and PDF. I would then like to keep the post from being displayed until I approve it. I think I can handle the approval process through base WordPress features but I can't quite figure out which approach to use for attaching files to the post. Is there any plugin or process you suggest for this? I'd appreciate any suggestions.