Double-sided proxy printing that actually lines up

How fronts and backs work in Fabricard

Duplex is a two-pass job: one PDF for the fronts, one for the backs, printed onto the same sheets. Three controls handle it:

Long-edge vs short-edge flipping

When the sheet turns over for the second pass, it turns around one of its two edges, and that decides which way up the backs come out:

• Long-edge flip: the sheet turns around its long side, like a page in a book. On a portrait A4 card sheet the backs stay upright. This is what you want.
• Short-edge flip: the sheet turns around its short side, like a notepad. On portrait paper the backs come out upside down relative to the fronts.

Card faces are close to symmetric top-to-bottom in position but not in content, so an upside-down back is obvious the moment you sleeve a card. For the portrait A4 sheets Fabricard exports by default, flip on the long edge: if you re-feed the paper by hand, turn the stack over sideways; if your printer duplexes automatically, pick "flip on long edge" in the driver. Either way, run the test sheet below before committing a full deck.

Page order and paper feed

1. Print proxies_fronts.pdf first, at 100% scale ("actual size" - never "fit to page", that changes the card size and ruins alignment on both sides).
2. Take the printed stack out and put it back into the paper tray for the second pass.
3. Print proxies_backs.pdf onto the same sheets.

The re-feed step is where most duplex jobs go wrong, because every printer pulls paper differently: some print on the face-up side of the tray, some on the face-down side, and some reverse the page order in the output tray. Find out once instead of guessing: take a scrap sheet, draw an arrow on it pointing away from you, feed it, and note which side got printed and where the arrow ended up. Also keep multi-page jobs in order - if your printer stacks output face up, the pages come out in reverse and you need to restore the order before re-feeding, or the backs of page 1 will land on the fronts of page 2.

The one-sheet test: measure before you print the deck

Never calibrate on a full deck. One sheet tells you everything:

1. Load your deck, leave Cut Guides switched on (they are on by default) - the corner marks are your measuring reference.
2. Export both PDFs as described above. In your PDF viewer's print dialog, print page 1 only of the fronts, re-feed that single sheet, then print page 1 only of the backs.
3. Hold the sheet against a bright light or window, back side toward you, and look at how the back images sit relative to the fronts shining through.
4. Measure the shift with a ruler, in millimeters, separately for horizontal and vertical - and check the top row and the bottom row separately, because many printers drift more toward the end of the page than at the start.

A shift of up to 3 mm is normal for home printers. It is also exactly what the next section corrects.

Fixing a 1-3 mm shift: Back Row Align

The Back Row Align block in the sidebar has six number fields: rows R1, R2 and R3 (top, middle, bottom row of the sheet), each with an X and a Y field. Values are millimeters, from -4 to +4 in 0.1 mm steps, and they nudge that row of cards in the export:

• Positive X moves the row to the right, negative X to the left - as seen on the printed back side of the sheet.
• Positive Y moves the row down, negative Y up.

So if your test sheet shows the backs sitting 1.5 mm too far left and 0.5 mm too high (looking at the back side), enter X = 1.5 and Y = 0.5. If only the bottom row is off, correct only R3 - per-row fields exist precisely because drift often grows down the page. Reset offsets under the block sets all six fields back to zero.

One thing to know: the offsets apply to whatever you export while they are set. They are meant for the backs run, so keep them at zero when you export the fronts. The preset buttons in the next section make that a two-click routine instead of something to remember.

Re-run the single test sheet after entering values. Two test sheets is the normal total; a stubborn printer might need a third.

Save it once: presets, and when to re-calibrate

Next to Back Row Align sits the Presets block with a Front and a Back column, each with a Save and a Load button. A preset stores the full layout state: paper format, card gap, bleed, all cut guide settings and all six row offsets. The routine:

1. With offsets at zero and your layout dialed in, click Save under Front.
2. After calibrating the back offsets, click Save under Back.
3. From then on: Load Front, export fronts, Load Back, flip backs, export backs. Done.

The calibration belongs to a specific combination of printer and paper. Re-run the one-sheet test when anything in that combination changes: a new printer, a different paper weight or brand, sometimes even a driver update. Presets live in your browser's local storage, like everything else in Fabricard - nothing is uploaded anywhere.