It turns out that I need that for a form, the sales order form in this case, only the footer is shown on the last page. Following these guidelines, I simply added an expression to the Hide property of the rectangle containing the items inside the footer to hide them on all pages except the last one. However, the form still reserves this space on the rest of the pages and I have blank spaces that are not being wasted.
As an alternative, and following several forums and information on the internet, what I did was to remove the footer and add the information it contained in a rectangle at the end of the body, with its respective expression in the hide property so that it is only shown at the end of the ssrs. The blank spaces are no longer a problem, but now this ‘footer’ does not appear fixed at the end of the page. Is there any way to do this? I have tried changing the position of the footer rectangle but as it is not fixed, the position is different every time I view a different report. I hope you can help me with this problem.