PDF background on top

i'd like to put the background in all pages, but i need that background on top.. Like the "stamp" but made with image or PDF file, is possible?

Because our management software have a bug that the text printed have a white background, so when we print over a background we have white box under the text. The software house that made the software says that the problem is not a bug, so we have to find a pdf creator that make background on top.

Best regards, Marco