A PDF can contain all the right pages in the wrong order. For an editable PDF on Mac, Preview lets you move pages using its thumbnail sidebar. Make a separate working copy first so you can return to the original sequence if you drag the wrong page.
Move thumbnails within the document
Open the working copy in Preview and choose View → Thumbnails or View → Contact Sheet. Drag the page thumbnail to its intended location in that PDF. Clicking a thumbnail merely navigates to the page; moving it changes the order.
For a simple three-page sample, start with Cover, Instructions, Checklist. Move Checklist between Cover and Instructions. The intended sequence is now Cover, Checklist, Instructions, and the file should still contain three pages. Avoid using Delete to move a page: deletion removes the page and its annotations.
Check the file you will share
Save the working copy, close it and reopen that exact file. Inspect the first page, the moved page and its new neighbors, then confirm the total page count. If the PDF contains printed page numbers or a contents page, check those separately against the new sequence.
Use the sidebar of the intended PDF rather than dragging between two open documents, which is a different operation. Keep the original and the reordered copy under distinguishable filenames. This verifies the actual saved document, not just the order visible in a window before saving.