what needs to be done:
1. Edit the background images
There's a file called "General background". This one has no page numbers. Take it and put in on all the pages in the file. BUT of course not the ones with a sepcific picture.
2. Those with specific pictures, different than the "General Background", you take them and delete the page number.
3. Place a automatic generated page number.
In Order if one double-page is deleted or added, page numbers will be still correct.
4. If possible, make the table of content numbers automatic generated too, in order to resemble any changes within the file. But this point is additional and not important, if it's something super complicated.