#641: print N-up sheets and folded booklets (#3916)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/control-protocol.md

@@ -181,3 +181,17 @@ and their parameter documentation. Search is case-insensitive across IDs, labels
 and parameter descriptions. Listing commands never discovers printers, submits a job or opens
 a dialog. Settings inspection is always available; submission becomes enabled when the native
 printer is ready, or when the browser host provides its print flow.
+
+### Physical print sheet layout
+
+`ui.printSubmit`, `ui.print` and `file.printPdf` accept `pagesPerSheet`: the integer
+1 (default), 2, 4, 6, 9 or 16, or `"booklet"` / `"bookletReverse"` for left/right binding.
+These settings change only the print PDF, leaving document Page Setup unchanged.
+Selection/range/parity are applied first. N-up fills cells in row order; booklet mode
+pads the selected pages to a multiple of four and pairs outer/inner pages. Copies
+repeat complete sheet plans, preserving blank slots at copy boundaries. Native copies
+remain a spooler setting. Two-up and booklet sheets are landscape. Use duplex on the
+short edge for folded booklets; this does not configure a printer's duplex capability.
+The preview shows physical sheet sides, before copies, using the same sheet plan.
+Explicit `paper` chooses the physical sheet; otherwise the first selected page supplies
+its size. Independent Page Setup multiple-page modes (#2414) are not required.