Last Edited September 28th, 2011
When a background is first dropped it takes on the page size of the page it is dropped onto and maintains that size from then on. Should you want to change the size of the page after dropping the background all you need to do is change the size of the background page as well for the background to fit.
This will work as long as you only have one page size per vdx. Should you have more than one page size per vdx you should create a background page per page size. This can be done by right clicking on the Insert > New Page... menu command which will bring up the following dialog:
When filling this dialog in you should not use any background and you should set its type as a background page before going to the "Page Size" tab and selecting your preferred page size, in this case A3:
Now proceed to drag a Process Background shape onto it and set any page of that size to that page size by selecting the page and going to "File>Page Setup", selecting the "Page Properties" tab and selecting the name of your new background page, in this case "A3Background" as shown below: