Placing documents into the public domain

Most rights can be voluntarily abandoned by the owner of the rights. Legislators can go to extra effort to create rights that can't be abandoned, but usually they don't do this.

In particular, you can voluntarily abandon your United States copyrights:

It is well settled that rights gained under the Copyright Act may be abandoned. But abandonment of a right must be manifested by some overt act indicating an intention to abandon that right. See Hampton v. Paramount Pictures Corp., 279 F.2d 100, 104 (9th Cir. 1960).

Micro-Star v. Formgen Inc., 154 F.3d 1107 (9th Cir. 1998).

You can also voluntarily abandon your European copyrights. You can't abandon certain reputation rights (such as the right to stop people from removing your name from your work), but you can abandon your copyrights.

The normal way to abandon a copyright is to make a clear written dedication of the work to the public domain. For example:

Most documents have a conventional location for a copyright notice (e.g., the bottom of page 1 of a scientific paper). You can write ``Public domain'' in this location rather than ``Copyright 2005,'' ``Copyright 2006,'' etc. This, by itself, clearly satisfies the ``overt act'' test.
You can write a subsequent document saying ``I hereby place my paper `On The Origin Of Species' into the public domain.'' This, by itself, clearly satisfies the ``overt act'' test.

I've seen a few people claiming, without justification, that a clear written dedication of the work to the public domain doesn't actually abandon copyright. Nobody, to my knowledge, has ever wasted a judge's time trying to make this silly argument in court.