nisus.com

CrisB wrote:[...] try it for a month (free of charge).

IIRC, it used to be one month quite sometime ago. Now the trial period is 15 days: Nisus Writer Pro FREE for 15 days! During the trial period a watermark will appear on the last page of any printouts. Once the trial period expires you will no longer be able to save documents, and the watermark will appear on all printed pages. http://www.nisus.com/free/pro.php
BTW somebody had requested the ability to use watermark as a feature. This should not be difficult, it seems!

Am I right in assuming that the new version 1.1 doesn't work with Panther any more? With Tiger at the office things are fine, but not with Panther at home.

That's correct, version 1.1 requires OSX 10.4 (Tiger) or later.