Find the reload direction
Download the duplex test from the same plan you intend to print. Print only its first PDF page. Mark the top edge of that sheet in pencil and note which side and edge enter the tray. Reload it, print only the second PDF page, then compare the FRONT and BACK marks.
If the back is upside down or on the same side, change the reload direction and repeat with a fresh sheet. Keep the working sheet beside the printer.
Keep the PDF order
In the refill builder, choose a double-sided arrangement even when you will feed the sheets manually. In the printer dialog, print each pass single-sided. This keeps the PDF’s binding margins and blank sides in the intended order.
Use the PDF page numbers, including intentional blank pages. Print the odd-numbered PDF pages first and the even-numbered PDF pages on their backs. Whether the second pass needs reverse order depends on the output tray and how you reload the stack.
Before printing a full pack, use a short selection with different dates on each page. Check that each intended front has the correct back. Do not remove blank PDF sides or tell the printer to skip blank pages.
Cut only after checking both sides
Keep copies separate. Check the page map in the refill builder before trimming an imposed set. A loose-page PDF and a two-up refill do not necessarily assemble in the same order.