Change the page size of a PDF, or scale its contents up and down. You can convert to a standard size - the A series from A0 to A6, plus US Letter and Legal - or keep the existing dimensions and apply a scale factor to what is drawn on them. This is what fixes a document that was laid out for Letter and needs to print on A4 without the edges being clipped.
Set the target page size to A4. The pages are resized and the content scaled to fit, which avoids the clipped margins you get from simply printing Letter artwork onto A4 paper.
With the page size left unchanged, it grows or shrinks the content within the existing page - so a factor below 1 pulls the content inwards and creates a wider margin.
No. Scaling resizes the whole page and everything on it. Cropping cuts away the area outside a selection and changes nothing about what remains.
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