Delete PDF Pages removes the pages you don't want and keeps the rest in their original order. Every page is shown as a small preview. Tap or click a page to mark it for deletion, Shift+click to mark a run of pages, or type the pages in the box (2, 5-7, 12-), and the two always stay in sync. Quick buttons select odd or even pages, invert the selection, or clear it, and a counter shows how many pages will remain.
The pages are removed from the original file in your browser with pdf-lib, so the title, author and other document details, bookmarks to the pages you keep, links and form fields stay as they were. The removed pages are taken out of the file completely, including their images and text, rather than just hidden, so the file gets smaller and the deleted content can't be recovered from it.
Honest limits: a PDF must keep at least one page, so you can't delete every page. Bookmarks that pointed at a deleted page stay in the outline but no longer jump anywhere. Password-protected PDFs and PDFs locked against editing have to be unlocked first. Files up to 200 MB are accepted.