This tool does one job well: it changes page order. It does not delete pages or duplicate them; removing unwanted pages, extracting a selection into a new file, or splitting a range belongs to PDF Page Editor. Keeping the scope narrow makes the safe path obvious — nothing is discarded by accident, and the original file is never modified because the output is always a fresh download. Pages are copied with their content intact, entirely in your browser.
Scanners often spit pages out in the wrong order, especially when scanning a booklet or a pile of receipts; this fixes the sequence before the document is shared. It is also the polite pre-step to Merge PDF: reorder the pages inside each part first, then combine, and the final file needs no post-production. For a scanned file with a stray blank or upside-down page, remove or rotate that page first, then arrange the rest here. The export is a brand-new PDF containing exactly the pages, in exactly the order, you approved on screen.
Also useful: PDF Page Editor, Merge PDF, and Split PDF.