A blank page from the scanner, a cover sheet nobody needs, page 7 of a contract that doesn't apply — removing pages is the most common PDF edit there is, and it shouldn't require desktop software.
Two ways to do it
If you know the page numbers, the Remove pages tool is fastest: type them in (single pages and ranges mix fine — 2, 5-7, 12), and those pages are gone. It runs entirely in your browser, so the file never leaves your device.
If you'd rather see what you're deleting, use Organize instead: every page appears as a thumbnail and you delete, rotate, or reorder visually. Same result, different workflow — numbers when you know them, thumbnails when you don't.
Keep instead of remove
When you want to keep three pages out of a hundred, listing the ninety-seven to delete is backwards. The Extract pages tool inverts the logic: list what stays, everything else goes.