In order to prepare a cover for print, we require the page count of your finalized PDF interior file. This number is used to calculate the width of the spine.

Do not use the page numbers in the footer to determine this, as they do not count the front matter etc.

Instead, look for the total number of pages in the document. Each application displays this a little differently. In the example below (macOS Preview and Adobe Acrobat Reader), the total page count of the document is 152 pages: