In short
This tool adds pages to an existing PDF, wherever you choose: an appendix at the end of a contract, a cover page at the start, blank pages for handwritten notes. Insert either all the pages of another PDF, copied with their text, images, size and orientation, or 1 to 100 blank pages, in the format of the neighbouring page, in A4 portrait or landscape, or in US Letter. The insertion goes at the start, at the end or after the page of your choice; to insert in several places, repeat the operation on the result. A password-protected PDF must be unlocked first. To reorder or duplicate pages, use “Organise pages”. The processing happens in your browser.