macOS Preview can reorder PDF pages — it's free and built-in. It's also slow with large documents and the thumbnail sidebar is small. For anything bigger than 10-20 pages, browser-based reordering is faster.
Here's when to use which.
Preview: built-in, fine for small jobs
Open the PDF in Preview, show the sidebar (View > Thumbnails). Drag thumbnails to reorder. Save. Works without internet. Best for 1-10 page reorders where the sidebar size doesn't matter.
Flint: faster, bigger thumbnails, bigger grids
Open reorder PDF in Safari/Chrome/Firefox. The thumbnail grid is bigger, the drag interactions are smoother, and operations like 'reverse selection' or 'move to position' are first-class. Better for documents over 20 pages or when you want to do batched moves.
The decision
Pages under 10, occasional reorder: Preview. Pages 20+, frequent reorders, complex moves: Flint. Either way, files stay on your Mac — Preview's local by default, Flint's local because the merge happens in your browser.
Don't double up
Reorder once. Don't reorder in Preview, save, then reorder again in Flint — you risk getting confused about which version is correct. Pick one tool per session, finish the job, save once.
FAQ
Does Preview support multi-select?
Yes, Cmd-click multiple thumbnails to drag them together.
Can I undo in Preview?
Cmd+Z works for most operations. Save when you're confident.
Why is Flint faster?
Bigger thumbnails, batch operations, no scroll-and-drag dance with a tiny sidebar.
Files leave my Mac in Flint?
No. Reordering runs in your browser. The PDF doesn't upload.
Preview for small jobs, Flint for bigger ones. Both local, both free.