Can I add guide lines or background elements to my Pages document to assist with layout?
Here is how I solved this:


Used a spreadsheet to choose values for all of the margins and four equal-height text boxes to best use the full 11" height of the printed page
Created four text boxes, full page width, and equal height
Used margins at the top of page, bottom of page, and between each text box, with all of these margins being of equal value
Used the spreadsheet to determine the exact starting Y location of each text box and enforce the desired margins
Pasted existing text into the four text boxes, using paragraph separation in some cases to combine the text from previously-separate textboxes into one textbox