About BackAlign and its method

BackAlign is an independent free tool for adults preparing their own printable cards, planner pages and similar PDFs. Its purpose is narrow: help diagnose whether one fixed front/back movement is appropriate, then create a separate print copy. It is not affiliated with Adobe or a printer manufacturer.

How it is made

The site and its explanatory material were developed with AI assistance. Its geometry, page selection and PDF transformations are checked with automated tests and browser inspection. AI assistance does not establish printer compatibility or commercial results. No physical print acceptance is claimed.

The calculation

One inch is 25.4 mm; an ordinary PDF point is 1/72 inch. A movement of m millimetres becomes m × 72 / 25.4 PDF points. Direct down movement uses a negative PDF y translation because normal PDF coordinates increase upward.

Guided measurements are observed through the front. The back coordinates reflect around the selected flip axis. Portrait long-edge and landscape short-edge setups reflect horizontally; the other two combinations reflect vertically. The tool converts that observation into a back-page movement. It does not mirror the artwork itself.

The four-mark diagnostic

The tool calculates a mean offset and the maximum Euclidean distance of a corner reading from that mean. A result above 0.5 mm blocks guided export. This threshold is a tool heuristic. Repeated physical proofs and the printer’s own documentation are more authoritative than a numerical result here.

What the PDF output preserves

The output uses the same full-page dimensions and embeds original page content as vector PDF content. It is intended as a print copy. Interactive input, rotated or cropped pages and mixed-size jobs are rejected; document navigation and accessibility structures are not an archival output contract. Source files are never overwritten.

Content and corrections

Guides use original worked examples and link to supporting references. Corrections to the calculation or a supported-file failure should be reported through the contact page. No fabricated customers, traffic or revenue figures are presented. First release: 28 October 2026.