Upload the GC design once — it tiles across A4 pages with an auto-incrementing number.
"Fit whole image" shows the entire photo with no cropping (may leave a small margin if its shape doesn't match the tile). "Fill tile" crops the edges to remove any margin. Rotate fixes a sideways/upside-down photo; zoom and pan reframe it.
Drag the highlighted number on the first tile in the preview to reposition — it moves the number on every tile at once. Or type exact mm values above.
A random 3-letter + 3-number code, unique per GC, printed at 50% opacity. Drag it anywhere on the first preview tile to reposition it on every tile at once — or type exact mm values below. Keep the code list to check against the GC number later.
With "Match tile shape" on, tile height is calculated from your photo's own proportions, so it fills each tile with zero empty margin — Rows becomes automatic and that field is ignored. Turn it off to set Rows manually instead.