"Print one picture on 4 pages" is the version of this question most people actually ask, so here is the direct answer: two sheets across by two sheets down, printed at 100 percent scale, trimmed on the cut lines and taped from the back.
The sheet count is not usually something you choose directly. You choose the width, or the sheets across, and the rows follow from the shape of the picture. A wide image across two landscape Letter sheets comes to 9 sheets (3 across × 3 down). A taller crop of the same picture will need another row. The tool shows the arrangement before you export, written as sheets across by sheets down, so you can adjust rather than discover it at the printer.
Common layouts, and what they get you. Two pages doubles one dimension. Four pages, in a two by two, doubles both. Six pages is either two by three or three by two depending on the shape. Nine pages is three by three and is about the point where trimming starts to feel like a project.
Overlap is not optional in practice. Home printers leave an unprintable margin, so pages that butt up exactly will always show a gap. A few millimetres of repeated image on each sheet plus a printed cut line is what makes the joins disappear.
The PDF is built in your browser and your image is never uploaded.