Re: lpcjon2's post.
I am sure he meant well, but in my opinion you would be wasting your money.
If package is lost, you will have to prove the value. I think you would be hardpressed to prove a value of an old file to be anywhere near $300. The Post Office will not pay more than actual value for loss of something with sentimental value. Same as for an old photograph- (yes it may be irreplaceable).
Also, Delivery Confirmation means exactly what it says. At the time of delivery the mailman does scan the parcel. Yes, it may be scanned at various points along the transportation line. BUT, (if lost) in the end you will be able to track it right up to the point where it was last scanned. And then the clerk will look at you and say "I am very sorry, but I don't know what happened to your parcel".
I am a retired Postmaster of a Sectional Center Office. I have handled a lot of claims over the years. It may not sound like it, but I do choose the USPS for all my shipping; I think it offers a great service for the price. If the item is irreplaceable I will use Registered Mail, which automatically includes insurance, (unless you refuse it) by the way. If not irreplaceable, I just send it insured for the appropriate amount.
Good luck and I hope you get better service next time.
Gary