Short answer: pick 2-up, 4-up or booklet, choose the paper and download. Pages are embedded, so text stays selectable and images keep their quality; a booklet pads the document to a multiple of four and tells you how many blank pages it added.
Why a booklet is not just “two pages per sheet”
A folded booklet prints page 1 and the last page on the same side, because the sheet is folded in half and the outer face is what you see first. Imposing that order by hand is the part people get wrong. The tool computes it, so duplex printing with “flip on long edge” and a single fold produces a document that reads in order without any page shuffling afterwards.
When 4-up looks bad
Four A4 pages on one A4 sheet is a quarter scale: fine for a slide deck you will read at a desk, poor for anything with 8 pt footnotes. If the text matters, 2-up is the honest choice; if you only need an overview, 4-up halves the paper again.