how, in Pages, when I have 20 pages and I want to change page 5 for page 1?

Word processing document:

COPY the contents of Page 1.

Place the insertion point in front of the first letter on Page 6.

Paste.

If needed, insert a page break at the end of this text to push the (originally) Page 6 text onto Page 7.

Select the contents of Page 5.

CUT (command-X) the contents of Page 5.

Select the contents of Page 1.

Press delete, then Paste. (command-V.

If needed, insert a page break at the end of this text to push the (originally) Page 2 text onto Page 2.

Page Layout document:

Click the View button to show Page Thumbnails in the left sidebar.

Select the thumbnail for Page 1.

Drag it down the sidebar, and drop it between pages 5 and 6.

Select the thumbnail for page 5 (now Page 4).

Drag it up to the top position in the column, then drop it in that top position.

Regards,

Barry