Here's a brief experiment using a graphic object as the 'page'.
As composed on US Letter with 0.5" margins, no headers and no footers.
Image was then copied to a second page. Shown as it would print at one page per sheet of US Letter.

Set to print two pages per sheet, the preview showed the same wide top and bottom margins as your example, so…

I opened a new document, set the paper size to US Legal and orientation to Landscape.
Using the same image(s), scaled to fit in the 7.5" height between 0.5" margins top and bottom, but maintaining the same aspect ratio as the original image, left some excess space in the gutter between the images when the outer edges were placed 0.5" from the vertical edges of the sheet.

In the image above, I've moved both images slightly closer to the centre of the sheet to leave 0.66" margins and a 1.33" gutter between them
These measurements are approximate; the goal is to split the total space available into four equal parts—one at each margin and two between the 'pages' which will be split into twomargins when the pages are separated. As can be seen, I didn't spend the time to get it exactly right.
Regards,
Barry