On the Page tab of File>Page Setup, there is a Scaling option that allows you to print using a percentage or a number of pages (wide or tall). When you use the Fit To option, to specify a number of pages, Excel ignores your manual page breaks. I don’t know about you, but that’s not usually what I want to happen.
I don’t know a good way to get around this, but if the layout of your page doesn’t change too much, there is at least one solution. When you scale using Fit To, Excel calculates the percentage that it has to shrink your print area in order to meet the Fit To conditions.
By specifying the Fit To, you can re-enter Page Setup, see what percentage Excel has calculated, and use that percentage. In the above example, I set Fit To to 1 page wide by 1 page tall. I closed out Page Setup and went right back into it. Excel figured that it would take a 59% scaling to get it on one page, and I switched option buttons back to Adjust To %. Now my manual page breaks are recognized.