How do I print and assemble a PDF pattern?

Print at actual size with page scaling turned off, and check the test square before printing the rest.

The single step people skip. Every PDF pattern has a test square or calibration box, usually on the first page. Print that page alone, measure the square with a ruler, and only continue when it measures exactly what it claims. Set the print dialogue to 100 per cent, actual size, or no scaling — never fit to page, which quietly shrinks everything by a few per cent and produces a garment a size too small.

Choose your layer. Most modern PDFs have layers so you can switch off every size but yours. Open the file in a reader that supports layers and turn the others off before printing. It saves ink and removes tracing errors.

Assembly. Pages are arranged in a grid with row letters and column numbers, and each has trim lines and registration marks. Trim two edges of every page — usually the top and the left — so each sheet overlaps its neighbour consistently. Work in rows: tape one complete row together, then join the rows. Match the registration marks rather than the paper edges, because printers are not perfectly aligned.

Use matte tape so you can still write on the joins.

The alternative is copyshop printing. Most PDF patterns include an A0 file intended for a print shop. It costs a few pounds per sheet, arrives as one piece, and removes the assembly entirely. For a large pattern this is usually worth it.