Why page size matters
A PDF carries its own paper size, and it doesn't always match the paper in your tray. A document made in Europe arrives in A4 and an American printer expects Letter; a form from the United States comes in Letter and a portal elsewhere asks for A4; a scan saved at an odd size prints with cut-off edges or big blank strips. Some printers stop and ask for the right paper, others crop the content.
Resizing the PDF puts every page on the size you need before you print or submit it. It is also the quick way to make a set of files consistent, for example when you merge documents from different sources and want them all on the same paper.
Available sizes
You can choose A4 (210 × 297 mm), Letter (8.5 × 11 inches), Legal (8.5 × 14 inches, the size also called Oficio in several countries, 21.6 × 35.6 cm), Oficio México (21.6 × 34 cm), A3, A5, or a custom width and height in millimeters for a template or a special format.
The orientation of each page is respected. Portrait pages get the portrait version of the new size and landscape pages get the landscape version, so a report with a few wide tables keeps those pages sideways.
Scaled to fit, never distorted
The content of each page is scaled as a whole, keeping its proportions, and centered on the new page. Nothing is stretched or squashed. When the shape of the old page and the new one differ, for example Letter to A4, you will see a thin white band at the top and bottom or at the sides; that is how the content stays undistorted.
If you want room around the content, for binding, for a stamp, or so that a printer that can't print to the edge doesn't cut anything, add the optional extra margin. The text stays real text, not an image, so it remains sharp, searchable and selectable. Links, form fields and annotations are lost, so keep the original if you need them.
In your browser, free
The pages are rebuilt in your browser. The PDF is not uploaded to a server and nothing is stored, which suits contracts, invoices and personal paperwork. There is no account, no watermark and no limit on use, on a phone or a computer.
If what you want is to fit several pages on one sheet, “Pages per sheet” does that. To cut away margins instead of changing the paper, use “Crop PDF”. Password-protected files need “Unlock PDF” first.