Get the front and back closer.

Measure a consistent duplex-print offset, then move only the back pages of your PDF. Free, local processing. No account.

Start with one calibration sheet. A fixed shift helps only when the offset repeats consistently.

Match your print setup

Calibration paper

OrientationDuplex flip

Enter the difference

How are you entering it?

Right (+) / left (−), mmDown (+) / up (−), mm

Compare all four corner marks

Save or reuse settings

Retest when printer, paper, tray, orientation, scale or flip changes. Settings contain no PDF content.

Open settings JSON

Your measured correction

Movement, not mirroring

Move PDF right / left0 mm

Move PDF down / up0 mm

Two pages, one sheet. Print at Actual size / 100% with the selected flip. Check the 50 mm ruler, then compare the five marks.

Make a corrected print copy

No PDF open

Choose a printable PDFUp to 30 MB · 200 pages · no password or interactive fields

Input file stays on this device.

Guided measurements move even-numbered backs in a front/back interleaved PDF. Direct mode offers other page selections.

A new print copy preserves vector artwork and page dimensions. It does not repair skew, scaling or inconsistent feeding. Content moved past a page edge can be clipped. Inspect the copy and print one proof first.

Supported PDFs and limits

Unencrypted, uniform-size, unrotated pages with an ordinary full-page crop. Annotations, links, forms, signatures and non-standard page units are rejected. The output is a print copy; bookmarks, tagged-document semantics and archival structures are not preserved. Keep the original.

Get a useful proof before a full batch.

Why double-sided printing does not line up
Diagnose a consistent offset, skew, scaling and changing paper-feed error before correcting a duplex PDF.
Long-edge vs short-edge duplex printing
Understand how page orientation and flip direction change the sign of a back-page correction.
Shift even PDF pages by millimetres
Move back pages for a duplex print job without resizing pages or rasterizing vector artwork.
Print a PDF at 100% without changing its size
Check paper size, scaling and borderless expansion before measuring a duplex printing offset.

What this tool actually changes

BackAlign applies a measured translation to selected page positions. It creates a separate PDF with the same page dimensions and embeds the original vector page content at the new position. It does not rasterize pages, contact your printer, or verify physical alignment.

Recognize the right kind of problem

Compare all four corner marks. If they differ in direction or by a substantial amount, check scale, paper feed and skew before moving content. The optional four-mark check uses a 0.5 mm variation threshold as a planning heuristic, not a printer tolerance.

A small example

With portrait paper and long-edge flip, a back mark that appears 2 mm right and 1 mm down through the front calls for +2 mm right and −1 mm down in the back PDF’s own view. The sample file and live diagram illustrate this calculation; they are not measurements of your device.

Read the method and release scope. No advertising or analytics runs in the PDF workspace.