In short
This tool rearranges the pages of a PDF, shown as thumbnails: putting a jumbled scan back in order, removing a blank page, turning a page scanned upside down the right way up. Move pages by dragging and dropping, rotate, duplicate or delete them, insert a blank page in the format of its neighbour or reverse the order of the whole document, then save a new PDF; the original stays untouched. The pages are copied without recompression and an existing rotation is kept. The document's title and author are carried over, but not its bookmarks. The tool works on a single PDF: to combine several, merge them first; to add pages from another file, use “Insert pages”. Everything happens in your browser.