PDF dimensions are only one part
The output records dimensions in PDF points. A viewer, printer driver or projector can apply another scale. Choose Actual size for printing and verify a known dimension with a physical ruler.
Measure both directions
Measure horizontal and vertical distances on the surface where the fabric will lie. Perspective distortion or a tilted projector can make one direction correct and the other wrong.
Recheck when the setup moves
Changing throw distance, browser zoom, display resolution or projector angle can change the scale. Repeat the measurement whenever the physical or display setup changes.
Verify a physical reference before cutting
Start at 100 percent scale unless the pattern's instructions require a deliberate change. Download the separate calibration PDF and print it at actual size, with fit-to-page and shrink options disabled. Measure the 100 mm reference using a physical ruler. A correct on-screen ruler or a viewer zoom label does not establish the printer's actual output scale.
The calibration page checks the print pipeline, while the stitched pattern must also be checked against its own known measurement or test square. The workbench's scale setting changes all geometry in the stitched page. If you intentionally choose 50 percent, the pattern dimensions halve; that does not automatically represent a valid garment-size change or preserve a pattern maker's grading rules.
For a large joined page, use a printer or print service that can accept its actual dimensions, or a PDF viewer's deliberate poster-tiling workflow. Do not let an automatic fit option reduce the entire pattern to one sheet without noticing. Confirm both horizontal and vertical reference dimensions, particularly if the source was scanned or previously resized.
Print a critical section before using expensive material. Compare matching marks, seam allowances and a known length with the original instructions. The output is a geometric assembly, not a certification of fit or sewing accuracy. Keep the source, chosen settings and verified print together, and stop if the calibration or a source reference differs from its expected physical length.