Do you mean within SiteSpinner at design time or when viewed in a browser?
Within SiteSpinner, you set the designed page length via the Options->Project Options... Target Resolution settings. You can then use the Arrange->Align->Bottom (or the ALT+Down Arrow shortcut, or the "to bottom" position button on the bottom toolbar) to put the object at the bottom of the designed page.
If your pages will vary in length (as most will), you can use set a tab guide on the vertical ruler below the designed target length and the bottom positioning tools will use it in addition to the page bottom.
Unfortunately, there is a limit to the number of tabs you can have per page (5 I think) and this only works to position objects one at a time per page.
If you need to do this as the object is displayed in the browser... well, if you can find a way that is compatible for all browsers, you can get rich.
What I am trying to do is place the 'Spun with SiteSpinner' logo (with link) a disclaimer notice, and copyright statement at the bottom of every page. You are right in assuming that my pages all vary in length. I have been looking for a 'footer' or similar but had no luck. I remember reading in the tutorial that it has to do with how I choose to copy, but can not find the tut page again.
I think you want Help->Tutorials->Objects, Components, Clones.
You probably want to go with a cloned object as that will allow you to use the same object, but at different positions on every page. An include places an object at the same position on every page.
If you can use a title object for your disclaimer and copyright notice, then you can make a permanent group of your three objects and if you turn re-render on, you will get a single object published for each page.
