When You Need to Merge PDFs with Different Page Sizes
It's common to encounter mixed page sizes when compiling work or academic materials.
- Combining an A4 report with A3 diagrams into one PDF
- Merging portrait text documents with landscape slides
- Mixing letter-size (US) and A4 (international) pages
- Scanned PDFs that differ slightly in size from digitally created PDFs
In these cases, you might worry: "Will merging force all pages to the same size?"
PDFnite Preserves Original Page Sizes
PDFnite's merge tool preserves the original size of each page. A4 pages stay A4, A3 pages stay A3 — all combined into one PDF.
This is possible because the PDF format itself allows pages of different sizes within the same file. PDFnite respects this specification and never forces pages to be resized.
In short, mixed portrait and landscape pages merge without any layout issues.
How to Merge with PDFnite
- Open the Merge PDF page
- Drag and drop all your PDFs — different sizes are fine
- Confirm the order (drag to reorder if needed)
- Click the "Merge PDF" button
- Download the merged PDF
All processing happens in your browser. Files are never sent to a server, so even confidential business documents are safe to use.
If You Want to Standardize Page Sizes
Sometimes you may want uniform page sizes in the merged PDF — for example, if you need everything to print on A4 or Letter paper.
Method: Use the Unify PDF Page Size Tool
Unify PDF Page Size resizes every page of a PDF to A4, A3, Letter, or Tabloid (11×17 in). Add several PDFs of different sizes and they are merged in the order shown while being resized, so merging and standardizing happen in one step.
- Open the Unify PDF Page Size page
- Drag and drop your PDFs (several are fine). As soon as they're added, you'll see which sizes are mixed — for example "A4 portrait — 12 pages / A3 landscape — 2 pages"
- Choose the paper size (A4, Letter, etc.) and orientation
- Click "Unify page size" and download
Each page keeps its aspect ratio and is scaled up or down to fill the paper, centered. If portrait and landscape pages are mixed, "Make orientation match" turns the pages in the minority 90° to fit. Keep in mind that fitting a larger page onto smaller paper makes text and graphics smaller (A3 to A4 is about 71%), and that resized pages don't keep their links or annotations.
| What you want | What to use | Page sizes |
|---|---|---|
| Combine, keep sizes | Merge PDF | Unchanged |
| Make every page match | Unify Page Size | A4, Letter, etc. |
| Match without a tool | Print → Save as PDF | Chosen paper |
Without a Tool: Re-export Using the Print Function
You can also open the PDF in a browser or PDF viewer, choose "Print" → "Save as PDF", set the paper size to A4 or Letter, and enable "Fit to page" (or "Scale to fit"). Setting names and behavior vary by viewer, though, and with mixed portrait and landscape pages some pages may end up turned.
Things to Know About Mixed-Size Merging
- For screen viewing, mixed sizes are fine: PDF viewers automatically adjust to each page's size
- For printing, check your printer's paper settings: For mixed-size PDFs, selecting "Fit to paper size" in your printer settings is recommended
- Scanned PDFs may have slight size variations: Scanner settings can result in pages that aren't exactly A4, but this doesn't affect merging
Frequently Asked Questions
Will pages be scaled up or down during merging?
No. PDFnite's merge tool preserves the original size of every page. No automatic resizing occurs.
Can I mix portrait and landscape pages?
Yes. Portrait and landscape pages can coexist in the same merged PDF, with each orientation preserved.
Will margins or content change after merging?
No. The merge process makes no changes to page content or margins. The original PDFs are concatenated exactly as-is.
Can I make every page the same size after merging?
Yes. Unify PDF Page Size resizes every page to A4, A3, Letter, or Tabloid. Add several PDFs and it merges and resizes them in one step.
Can I merge PDFs with different image resolutions?
Yes. In PDF format, resolution is a property of individual images rather than the overall page. Merging files with different resolutions has no impact on quality.
Summary
For merging PDFs with different page sizes, PDFnite preserves each page's original size without any forced resizing. Mixed A4, A3, letter, portrait, and landscape pages all merge without issue. If you want every page on the same paper size instead, Unify PDF Page Size merges and standardizes in one step. Both are free and require no installation.