Word Online does not show background images that have been added on the Desktop client with Design>Page Color>Fill Effects....
Alternatively, I tried to add a normal image to the header (behind text), which also is not displayed in Word Online.
The use case is that my client does want the background image to show up when saving to PDF, but they do not want the background image to print on paper. This has always worked with Word on the Desktop, but it doesn't work when using Word Online.
My client heavily relies on that functionality.
How do I add a full-page background image to our Word Online documents, that are shown in the browser, shown when saved to PDF, but not shown when printed on paper directly from Word Online?