Crop PDF, Add Margins & Resize to A4

About Crop PDF, Add Margins & Resize to A4

A PDF page can carry up to five rectangles that define its size: the required MediaBox (the whole sheet), the CropBox (what viewers and printers show), and three for print production — the BleedBox (area including bleed), the TrimBox (finished size after cutting) and the ArtBox (extent of the meaningful content). By the specification, a missing CropBox equals the MediaBox, and the other three default to the CropBox.

Most PDF “cropping” is just changing those numbers. Besides the crop mode, where you choose which box to change, this tool offers tabs for adding margins, fitting pages onto A4 or Letter, and extending bleed. The crop mode only edits numbers; the other three place the original page onto a new sheet or redraw it.

What CropBox hides is still in the file

The default mode shrinks the CropBox. Viewers clip the page to that rectangle, but the text and images in the content stream don’t change by a single byte. That makes cropping reversible: any editor that removes the CropBox or resets it to the MediaBox brings the cut-off area straight back, and the file barely gets smaller.

That cuts both ways. It’s ideal for hiding the black strip around a scan with no quality loss. But “cropping away” a Social Security number or signature next to a table is not removal — the recipient can recover it, and some viewers still include the hidden text in search or copy. For anything that must be gone, use the redaction tool, which deletes the content itself.

Cropping again works from what is visible now — the overlap of the current CropBox and the MediaBox. Crop 10 mm off every side, then enter 5 mm, and 15 mm is gone relative to the original. On rotated pages (/Rotate 90 and so on), enter top, bottom, left and right as the page appears on screen; the tool maps them back to the unrotated coordinates.

When to pick MediaBox, TrimBox or BleedBox

MediaBox mode shrinks the sheet itself. Because no other box may extend beyond the MediaBox, the tool clips any existing CropBox, TrimBox, BleedBox and ArtBox to the new MediaBox. It’s useful when an older program or print driver ignores the CropBox and only reads the MediaBox — but it still doesn’t delete content.

TrimBox and BleedBox don’t change what you see on screen. A print shop reads the TrimBox as the cut line and the BleedBox as the output area including bleed. For a US business card ordered as 3.5×2 in finished with 1/8 in bleed, the MediaBox would be 3.75×2.25 in and the TrimBox the inner 3.5×2 in. If the viewer looks unchanged, that’s expected; the page-boundary report in the PDF info tool shows the actual values.

Fit to A4 or Letter

Print an A4 document from a European client on US Letter and the printer either shrinks it unevenly or cuts off the bottom. The fit mode creates new pages at the paper size you choose and centres each original page on them, keeping its proportions. The original goes in as a form XObject — a reusable drawing, not a picture — so text stays selectable and vectors stay sharp.

Annotations such as links and comments are moved to the new coordinates, and internal links are re-aimed at the new pages. Form fields can’t be carried over this way; they’re dropped and the result screen says how many. Flatten the form first if the answers matter. Scale and position can be adjusted page by page, handy for one scan that was placed crooked on the glass.

Adding margins and a binding gutter

Margin mode makes each new page the visible size plus the margin on every side and centres the original content on it. Content is not shrunk; the paper grows. It’s for giving an edge-to-edge PDF room for notes, or keeping content clear of the unprintable edge. Add a gutter and it goes on the left of odd pages and the right of even pages, so in a duplex booklet bound on the left, the bound edge of every sheet is the wider one.

Extending bleed for a file made without it

Designs with colour running to the edge of the paper need 2–3 mm (about 1/8 in) of extra artwork beyond the trim line so small cutting errors don’t leave a white sliver. This mode takes pages with no BleedBox, or one equal to the MediaBox, renders them at 150 or 300 dpi (your choice), reflects the edge pixels outward by the width you set (3 mm by default), and records the original size as the TrimBox.

The cost is real. A processed page becomes a single JPEG, so its text can’t be selected, and the default 150 dpi may be too coarse for fine print. Choosing 300 dpi sharpens text at the cost of a file about four times larger. Pages that already have bleed are left as vectors. If you have the original design file, adding bleed there and re-exporting is always better; this mode is the fallback when you don’t.

Worked examples

How to use it

1. Load a PDF and pick a tab: crop, add margins, fit to paper, or extend bleed.
2. For cropping, drag the area to keep on the preview or type the margins in mm, then choose the box and page range.
3. Check the preview and download the PDF.

Frequently asked questions