Confluence currently doesn't have the option to add watermark or custom notes in header or footer for printouts.

In some cases, users would like to add a note such as "Confidential" or "Internal use only" on the top or bottom of the printout which is not currently possible at this moment.

Possible workaround

As a workaround It is possible to modify the layout and use CSS to show the notes only on the printouts, see example below:

1. Go to Space Tools >> Look and Feel >> Layout >> Next to Main layout, Create Custom then Edit the main layout
2. Insert the code and save
   after:

   #if ($useNewSpaceIA && ($decoratorUtil.hasSidebarContext() || $sitemeshPage.getProperty("page.ia-sidebar")))
   </div>
   

   Insert the following in a new line

   <div class="confhid">** Confidential ** Confidential ** Confidential ** Confidential ** Confidential **</div>
   

1. Go to Look and Feel >> Stylesheet >> Edit >> insert the following and save:

   @media screen {
   .confhid {
   display:none!important;
   }
   @media print {
    display:inline-block!important;
   }