Secure Digital Vault

I have an internet site which I am developing as part of a new document solutions business. As part of this I want to create a digital vault where I can upload documents and my customers can then go in, using a username and password that I can administer, to search, view and download their documents.
When a user logs on they should be granted access only to their files. I would like to give the user the ability to search the files by name, date, author or keyword.
The files would be PDF format.
I would also require an administrative section to allow me the ability to upload the files and delete and move them as neccesary.