PDF scale corrector

Print at Actual size or 100 % first and measure the test square. If it is still off, the printer itself prints slightly small or large. A desktop print dialog with a Custom scale box can apply one percentage; this tool is for everything else: a phone or tablet with no scale setting, a copy shop, a printer that is off by a different amount across and down, or a file you want corrected once and printed many times.

They are set by different parts of the printer: the paper feed moves the sheet down the page, the print head or laser scans across it. A worn or slipping feed roller shortens the page in one direction only, so a square can come out 100 mm across and 98.8 mm down. The tool corrects each direction by its own factor; enter the same reading twice if both are equal.

Choose inches, enter 4 as the length it should be and 3.875 for what you measured (1/8 in = 0.125). The correction is 4 / 3.875 = 103.23 %. An error that large is more often a setting than the printer: Fit to page or Shrink oversized pages reduces a page by about 3 to 6 % on A4 or Letter, so turn it off and measure again before correcting. If the square is still short at Actual size, correct the file.

Keep page size draws the corrected content centred on a page of the original size. When the correction enlarges, the outer band moves past the edge: 1.42 % on A4 is 1.5 mm each side, inside the margin most printers cannot print anyway, and the tool shows the band. Enlarge the page scales the page with the content, so nothing is cut off, but an A4 page becomes about 213 × 301 mm; print it on A4 at Actual size and that outer band is cut off by the paper instead.

Yes. Each page is placed into the new file as it is, scaled, with its text and lines still vectors — nothing is turned into an image, so a pattern stays crisp at any size. Links, form fields and comments are not carried over; the printed drawing is.

No. The file is read, rewritten and saved in your browser and is never sent anywhere. The share link carries only the reference length, your two readings, the unit and the page option — the settings of your printer — never the file or its name.

Use the longest reference you have and a good ruler: half a millimetre on a 100 mm square is 0.5 %, which is about the smallest error worth correcting. Measure from outer edge to outer edge, on the same paper and printer settings you will print with. A correction made for one printer, paper size and tray does not carry over to another.

Readings more than 10 % from the reference, which come from a wrong setting or a wrong reference rather than printer drift; password-protected PDFs, which cannot be rewritten without the password; and pages that use a non-standard page unit. Every page of the file is corrected by the same factors, up to 500 pages.