The FSF publishes some GNU manuals in printed form. To encourage sales of these manuals, the on-line versions of the manual should mention at the very start that the printed manual is available and should point at information for getting it—for instance, with a link to the page http://www.gnu.org/order/order.html. This should not be included in the printed manual, though, because there it is redundant.
It is also useful to explain in the on-line forms of the manual how the user can print out the manual from the sources.