What is the best solution for document archiving?

Solution 1:

you can dedicate an old PC (with big new HDD/s) as a backup server and install BackupPC

• No client-side software is needed - just export via NFS backup dirs on the clients (for example /home/ or /home/username/Desktop etc.) or share folders on Windows stations
• A powerful web user interface allows administration, view log files, configuration
• file extensions can be defined for including / excluding files
• uses rsync for fast backup

separately you can implement web search on the linux server using Xapian or Omega

Solution 2:

You can use a cloud computing services like Dropbox or UbuntuOne

I advise you tu use Dropbox, you can choose between free(2gb+8by invites other people) or paid plan (50 or 100gb).

You can share folders with other dropbox user or in read only way with anyone.

And restore deleted files