How to insert page numbers in Footnotes of existing document

When I insert page numbers into the footnote areas of my document, the existing text (within the pages) gets moved. i.e. as though space is inserted between the lines, moving them to the following page.
Is there a way around this so I can add my page numbers to the footers WITHOUT any existing document text being changed?

By design (I’m not saying that it is a good design, just describing how everything works) on Writer headers and footers belong to the text area so when you add them the portion of the page devoted to the “real” text gets reduced. The only workaround is to reduce the bottom margin by hand. You’ll probably need to force the footer height to a fixed value and then reduce the bottom margin by that value in order to get what you want. See the Footer tab on the page style definition.

Thanks a lot for that - I’ll give it a go !

Is there a way to make this persist throughout the rest of the document? Or make it a template so that future documents are always this way?
Thanks

Say she has a 200 page novel with no page numbers and wants a sanely easy way to insert numbering on all pages without doing each page separately.

This is not an answer and should have been a comment.

It is also a duplicate of question 148040.