Add a Background to a PDF

You can add a background to a PDF in Acrobat, and set that background to appear only when printing, only onscreen, or both. Here’s how: choose Document> Background, select a color from the color picker, or browse to a file you want to insert as a background, and set its opacity, scale and position. 

Then click Appearance Options in the Appearance area of the dialog box. There, you can control whether the background appears on screen, when printing, or both. The possible uses for this are mind-boggling.