IMPORTANT: Before doing anything you have to plan if you are adding the same page background to all pages or if you want to add a page background to some page only.
Adding the same page background to all pages: set the Make changes to All Elements' button to ON (2) - see image below.
Adding a page background to one page: set the Make changes to All Elements' button to OFF (2) - see image below.
For this tutorial we are going to add a page background to one page only
1. Setting the Transparency for the Header and Footer Sections
Each content page has three sections: header, footer and content. Let's start by setting the headers and footer sections to have a transparent background.
Make sure you select the 'Page Header' container (1) and that the 'Make changes to All Elements' button is OFF (2).
Click on the color picker (3) in the background section and set it to transparent - move the transparency slider all the way to the left. (4), then click on Choose.
Repeat the same procedure with the footer, in the same exact order. Then click on Choose.
At this point, your page should look like this.
2. Adding the Image or Texture Background
VERY IMPORTANT: Please pay attention to this step. This is where many users click on the wrong place and end up adding the background image to the header section instead of the the whole page.
Make sure you click on the 'Regular Page' text outside the page (1) open the page toolbar (2) and click on the 'Set Page Image' icon.
The Image gallery on the left sidebar will open. If you have text on the page add an image with a light background.
If for any reason, the background image is too dark and makes reading the text difficult, add opacity to the page as explained in the tutorial below.