What is duplex printing?

Where the word comes from

The word duplex belongs to office printers and print drivers, where it names a setting rather than a kind of job. Print shops are more likely to say double sided, and quotes often describe the ink on each face, so full colour on both sides and full colour on one side are priced as separate lines. The printing standards spell the choice out plainly. The Internet Printing Protocol, published as RFC 8011, gives every job a sides attribute with three values: one-sided, two-sided-long-edge and two-sided-short-edge. Those three words are the whole vocabulary a printer needs, and they are worth knowing because the long edge and short edge distinction is where most double sided mistakes begin.

How the second side lines up

When a sheet is turned to print its back, it can flip along its long edge, like the page of a book, or along its short edge, like a wall calendar lifted upward. A portrait flyer read by turning it over sideways wants a long edge flip. Choose the wrong one and the back arrives upside down. Page layout software keeps track of which face is which through the idea of left and right pages, which the CSS Paged Media specification also defines for documents built on the web. On a desktop printer without automatic duplex, the manual method in Adobe's InDesign help is to print the odd pages, turn the stack and feed it back for the even pages. Print one test sheet first and mark the top edge with a pencil arrow before committing the whole stack.

When a back page earns its place

A second side pays off when the flyer is held in the hand. A letterbox drop, a handout at a market stall or a sheet left on a clinic counter all get turned over, so the front can sell while the back informs: a timetable, a price list, a map, the terms of an offer. A flyer pinned to a noticeboard or taped inside a window never shows its back, so duplex there is money spent on a face nobody sees. The same flyer posted to social media has no back at all, which is a good test of the front. If the front cannot stand alone, the back is propping it up. A useful split is to keep one promise, one image and one action on the front, then move everything a person needs only after deciding to act onto the back: session times, the full address, parking, fine print.

Common mistakes

The most visible one is the upside down back, caused by the flip setting rather than the artwork. The costly one is putting the call to action only on the back, so everybody who sees the front on a table misses it. Repeating the front headline on the back wastes the space that justified the second side. Thin paper lets a dark photo on one face ghost through the other. Sending two separate files without saying which is the front invites the shop to guess. And a folded leaflet is a different job from a flat double sided sheet: folds create panels with their own sizes, so a duplex file cannot simply be folded afterwards.

Making a two sided flyer in the builder

There is no duplex setting in the flyer builder, because a print driver or a print shop makes that choice. What the builder does is let one flyer hold several pages. A second page is added From Library, at the active page's size, or as a Blank page, which is always A4 portrait, and pages can be duplicated or deleted. The AI generator always returns a single page, so the back is added by hand afterwards. A PDF export includes every page, so a two page flyer becomes a two page PDF with the front first, which is the file most shops expect. PNG and JPG exports carry only the active page. Every page captures at twice the canvas, so A4 exports at 2480 by 3508 pixels. There is no bleed, no crop marks and no CMYK, so ask the shop how they handle an RGB file.

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