Resize a PDF

Resizing a PDF means changing the page, not the file size

This is the distinction worth getting straight first, because the same phrase is used for both and the tools are completely different. Resizing a PDF changes the physical dimensions of its pages: an A4 document becomes a Letter document, or a page laid out at some arbitrary size becomes a standard one. Compressing a PDF changes how many bytes it occupies and leaves the page dimensions exactly as they were. If your problem is an email attachment limit, you want compression. If your problem is a printer, a portal or a publisher that expects a specific page size, you want this page.

A4 and Letter, the mismatch that causes most of this

A4 is 210 by 297 millimetres and US Letter is 8.5 by 11 inches — 216 by 279 millimetres. Letter is about 6mm wider and 18mm shorter. That is small enough that a document looks fine on screen either way and large enough that printing an A4 file on Letter paper clips the bottom of the page, or leaves an odd band of white and a shifted margin. Anyone working across the US and almost anywhere else meets this regularly, and converting the file once is more reliable than hoping every recipient's print dialog scales it the same way.

What happens to the content

Each page is scaled to fit the new dimensions with its proportions preserved, and centred. Nothing is stretched, and nothing is cropped. Because the aspect ratios of A4 and Letter differ slightly, a converted page carries a thin margin on two sides — that is the correct result rather than a defect, since the alternative is distorting the page or cutting a piece off it.

The content is placed as a vector, so text stays text and remains selectable and searchable. It is not re-rendered into an image, which means no quality is lost going up or down in size, and the file does not balloon.

Orientation is followed by default

A landscape page resized onto a portrait sheet would be shrunk to a fraction of the available area. So each page keeps its own orientation by default: a landscape page in a portrait document gets a landscape A4 rather than a squeezed portrait one. Turn that off if you genuinely need every page the same way up — for a print run that will be bound, for instance.

Scaling to fit an existing size

The other common case is a document produced at some size nobody asked for — a design export at 1000 by 1000 points, a slide deck exported at 16:9, a page produced by a scanner that used its own dimensions. Choosing a standard size scales it to fit, which is usually all that is needed to make it printable. If the pages also need reordering or rotating before printing, do that first, then resize.

Next steps