How can I add a full background to an A4-sized Word document?

Question

I'm trying to add a background to an A4-sized Word document.What is the correct background image size (in terms of resolution) to put into an A4 document? I tried Watermark, Fill effects, and tried to put the image into the header as well. The image doesn't fit correctly – it will be centered and I need to scale it without causing a quality drop.

Answer 1

Page Layout > Page Color > Fill Effects > Picture > Select Picture.

Use Paint.NET, create image of 210x297mm with 200+dpi resolution and use this image as background. This should work.