Describe the bug
Using the new #9850 feature to specify a custom layout, the footer containing page numbers is not positioned correctly. The page content is also not scaled correctly to fit onto the page

To Reproduce
Steps to reproduce the behavior:

1. Add custom CSS as in feat: Enable PreferCSSPageSize option for PDF generation #9850 to force custom print layout

@media print {
    @page {
        size: A4 landscape;
    }    
}

3. Build and run docfx to create output that includes pdf settings like the following sample globalMetadata

    "globalMetadata": {
      "_appTitle": "On Key Release Notes",
      "_appFooter": "On Key Plus 2024.13.0 (Build 0)",
      "_appFaviconPath": "images/favicon.png",
      "_appLogoPath": "images/onkey_icon.png",
      "_enableNewTab": true,
      "_enableSearch": true,
      "_disableNavBar": "true",
      "_disableBreadcrumb": "true",
      "_disableToc": "false",
      "_disableAffix": "false",
      "pdf": true,
      "pdfTocPage": true,
      "pdfFileName": "onkey_releasenotes.pdf",
      "pdfPrintBackground": true
    },

Generated output

Notice that the page content is not scaled to fix onto the page (nr 2) and that the footer is not positioned correctly (nr 1) as illustrated above

Context (please complete the following information):

• OS: Windows
• Docfx version: 2.77.0