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Merge PDFs with different page sizes (A4 + Letter)

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It’s common to receive PDFs from multiple sources—one exported on A4, another on Letter, and a third scanned sideways. When you merge them, the goal is simple: one file, correct order, no surprises.

In this guide, you’ll use Merge PDF to combine documents with different page sizes. We’ll also cover what merging can (and can’t) change about page dimensions.

In this guide

When mixed page sizes happen

  • Application packets: ID scans (Letter) + forms (A4) + certificates (mixed)
  • International teams: templates created on different regional defaults
  • Old scans: rotated pages or inconsistent margins
Important: Merging usually keeps each page’s original size. If you need every page to become the same size (all A4 or all Letter), that’s a separate “resize pages” workflow.

Step-by-step: merge mixed sizes

  1. Open Merge PDF.
  2. Upload the PDFs you want to combine.
  3. Drag files into the correct order (top to bottom).
  4. Create the merged PDF and download it.
  5. Open the result and scroll through quickly to verify: order, orientation, margins.
Try Merge PDF

Tips for printing and consistency

1) Expect “mixed size” output

When you merge an A4 page and a Letter page, the merged PDF typically contains one A4 page and one Letter page—still different sizes. That’s normal and usually the best outcome for fidelity.

2) Use “Fit to page” when printing

If your merged document contains mixed sizes, set your printer dialog to “Fit” or “Shrink to printable area.” That prevents cropping when a Letter page is printed on A4 paper (or vice‑versa).

3) Compress after merging if the file gets large

Combining multiple scans can increase file size. After merging, run the result through Compress PDF to make sharing easier.

4) If a PDF is locked, unlock it first

Password-protected PDFs often can’t be merged until they’re unlocked. If you have permission, use Unlock PDF first, then merge.

FAQ

Will merging resize my pages?

No—merging generally keeps each page’s original dimensions. It combines pages into one file, but it doesn’t “normalize” them to A4/Letter.

Can I merge PDFs with different orientations?

Yes. Portrait and landscape pages can live in the same PDF. Just review the merged file to ensure everything reads correctly.

Does merging reduce quality?

Merging itself should not reduce quality. If you also compress the output, image-heavy pages may look softer depending on compression.

What’s the best workflow for a clean submission PDF?

Merge first, then add finishing touches like page numbers and (if needed) compression.

Next steps