Scale PDF from A4 to A3: how to do it correctly

Scale PDF from A4 to A3 and vice versa

2 min read·25 July 2026

Changing a PDF size — from A4 to A3 or the other way around — is a common need. Here are the options and pitfalls.

When you need to change format

Sometimes a document is created on A4 but needs to be printed on A3 (e.g. for large floor plans, technical drawings or posters). Or the reverse: you have an A3 document that needs to fit on A4 for a regular printer. Both directions are possible.

Resize with PDFrust

Use the Resize tool on PDFrust. Choose the target format (A3, A4, A5, Letter, etc.) and select the scaling method: "Scale content" (text and images are proportionally enlarged or reduced) or "Adjust page size only" (only the paper size changes, content stays in the same position). For A4→A3 choose "Scale content" for best results.

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Monitoring scale factor

A4 to A3 is a factor of 1.414 (√2). A3 to A4 is 0.707. For text documents this is fine — text remains readable. For drawings with a fixed scale (e.g. 1:50) the scale changes when converting. Always note the new scale after adjustment.

Alternative: poster tool for printing

If you want to print an A4 document at A3 size but do not have an A3 printer, use the Poster tool. This splits the A4 page across two A4 sheets that you can tape together. This gives you A3 format on a regular printer.

Margins after scaling

After scaling from A4 to A3 the margins may be too large. Use the Trim Margins tool to crop excess white space. Or use the Margins tool to adjust margins symmetrically for a professional result.