Can I merge PDFs that have different page sizes?

Yes — merging combines the files regardless of page size, and each page simply keeps its own dimensions in the result. So a merge of an A4 document, a Letter document, and a Legal document produces one PDF whose pages are a mix of those sizes. Nothing breaks; the content is all there. The only question is whether mixed page sizes are acceptable for your use, or whether you want them unified. So the merge itself is never blocked by size differences — page size is a property of each page, and a PDF can happily contain pages of different sizes. The decision is purely about presentation and printing.

Does it matter if the merged PDF has mixed page sizes?

For on-screen reading, usually not much — viewers just show each page at its size, and readers scroll through fine. It matters most for printing: a printer set to one paper size will scale or crop pages that do not match, so an A4 page sent to a Letter tray (or vice versa) may be shrunk, enlarged, or have edges clipped, and the document feels inconsistent. It can also look unpolished in a formal deliverable. So if the merged PDF is for screen, mixed sizes are often fine; if it will be printed (especially a formal or bound document), you usually want a consistent size. Decide by how it will be used.

How do I make all the pages the same size?

Normalize them — resize the pages to a single target size (A4 or Letter, typically). There are two ways: scale-to-fit, which resizes each page's content to the target dimensions (content may shrink/grow slightly and aspect-ratio differences can add margins), or pad-to-size, which keeps the content at its original scale and just enlarges the page box to the target, adding whitespace. Scale-to-fit gives uniform pages with content filling them; padding preserves exact 1:1 scale (important if dimensions matter). Pick your target size and method, normalize, then the merged document prints and reads consistently. So the fix for mixed sizes is a resize/normalize pass to one chosen size.

Will normalizing cut off any content?

It should not if you do it correctly — but it is the thing to watch. Scale-to-fit preserving aspect ratio fits the whole page within the target (adding margins where ratios differ) without cutting content; the risk of clipping comes from forcing a page into a different aspect ratio without preserving it, or cropping. So choose a normalize option that fits the content rather than crops it, and check the result — especially pages that were a very different shape (Legal is longer than Letter) — to confirm nothing important is lost at the edges. Padding never clips (it only adds space). After normalizing, verify a few pages, particularly any that changed shape significantly, before relying on the document.

Should I normalize before or after merging?

Either works; pick by convenience. You can resize each source PDF to the common size first and then merge (clean and predictable), or merge first and then resize the whole combined document to one size in one pass (fewer steps). Resizing-then-merging gives you control per source if they need different handling; merging-then-resizing is quicker when one uniform size suits everything. Both reach the same place: a merged PDF with consistent page sizes. For a simple "make it all Letter" job, merge then normalize the result; if sources need individual attention, resize each first. The order is a workflow preference, not a correctness issue.

What target size should I choose?

Match your audience and printing. In North America, Letter is the default; in most of the rest of the world, A4 — so choose the size your readers will print on, since printing a Letter-normalized PDF on A4 (or vice versa) reintroduces the scaling/cropping you were trying to avoid. Legal is unusual and rarely the right unifying target unless the content genuinely needs the extra length. So pick A4 or Letter by region/audience, normalize to it, and your merged document prints cleanly for the people who will print it. If the document is screen-only, the target matters less, but a consistent size still looks more professional.

Is it safe to do this with an online tool?

For confidential documents, prefer a tool that processes files locally. ScoutMyTool merges and resizes pages entirely in your browser tab, so your files never leave your machine. For anything sensitive, confirm the tool does not upload before using it — and check a few pages after normalizing to confirm nothing was clipped.

6 min read

How to merge PDFs with mismatched page sizes (A4 + Letter + Legal)

By ScoutMyTool Editorial Team · Last updated: 2026-05-22

Merging PDFs with different page sizes — A4, Letter, Legal — works without a hitch: the merge combines them and each page keeps its own size, so you get one document with mixed pages. Nothing is lost. The only real question is whether mixed sizes are fine for your use (often yes for screen) or whether you should normalize them to one size (usually yes for printing or a formal deliverable). This guide covers exactly that: why the merge is never blocked by size, when mixed sizes matter, how to normalize to a single size without cutting off content, and which target size (A4 vs Letter) to choose for your audience.

Three ways to handle it

Approach	When to use
Leave mixed sizes as-is	Screen reading; each page keeps full fidelity
Normalize to one size (scale to fit)	Consistent printing; uniform look
Normalize by padding (add margins)	Keep scale 1:1, just unify the page box

Step by step — merge mixed-size PDFs cleanly

Just merge — size won’t block it. Combine with Merge PDF (see merging PDFs); each page keeps its own size.
Decide if mixed sizes matter. Screen-only → often fine; printing or a formal deliverable → normalize to one size.
Pick a target size. Letter (North America) or A4 (most elsewhere) by your readers’ printing — not Legal unless the content needs the length.
Normalize the pages. Resize to the target with Resize PDF Pages — scale-to-fit (uniform, preserve aspect ratio) or pad-to-size (keep 1:1 scale, add margins).
Avoid clipping. Choose a fit-not-crop option; padding never clips.
Verify changed-shape pages. Check pages that were very different (Legal vs Letter) to confirm nothing important was lost at the edges.
Order before/after as convenient. Resize each source first, or merge then resize the whole thing — both reach a consistent document (see batch merging and cherry-picking pages).

Merge PDFs: the core combine guide.
Merge across operating systems: combining varied sources.
Batch merge PDFs: many files at once.
Cherry-pick pages: selecting pages to combine.
Merge from cloud storage: combining files from Drive/Dropbox.
Resize PDF Pages tool: normalize sizes in your browser.
All ScoutMyTool PDF tools: the full toolkit.

FAQ

Can I merge PDFs that have different page sizes?: Yes — merging combines the files regardless of page size, and each page simply keeps its own dimensions in the result. So a merge of an A4 document, a Letter document, and a Legal document produces one PDF whose pages are a mix of those sizes. Nothing breaks; the content is all there. The only question is whether mixed page sizes are acceptable for your use, or whether you want them unified. So the merge itself is never blocked by size differences — page size is a property of each page, and a PDF can happily contain pages of different sizes. The decision is purely about presentation and printing.
Does it matter if the merged PDF has mixed page sizes?: For on-screen reading, usually not much — viewers just show each page at its size, and readers scroll through fine. It matters most for printing: a printer set to one paper size will scale or crop pages that do not match, so an A4 page sent to a Letter tray (or vice versa) may be shrunk, enlarged, or have edges clipped, and the document feels inconsistent. It can also look unpolished in a formal deliverable. So if the merged PDF is for screen, mixed sizes are often fine; if it will be printed (especially a formal or bound document), you usually want a consistent size. Decide by how it will be used.
How do I make all the pages the same size?: Normalize them — resize the pages to a single target size (A4 or Letter, typically). There are two ways: scale-to-fit, which resizes each page's content to the target dimensions (content may shrink/grow slightly and aspect-ratio differences can add margins), or pad-to-size, which keeps the content at its original scale and just enlarges the page box to the target, adding whitespace. Scale-to-fit gives uniform pages with content filling them; padding preserves exact 1:1 scale (important if dimensions matter). Pick your target size and method, normalize, then the merged document prints and reads consistently. So the fix for mixed sizes is a resize/normalize pass to one chosen size.
Will normalizing cut off any content?: It should not if you do it correctly — but it is the thing to watch. Scale-to-fit preserving aspect ratio fits the whole page within the target (adding margins where ratios differ) without cutting content; the risk of clipping comes from forcing a page into a different aspect ratio without preserving it, or cropping. So choose a normalize option that fits the content rather than crops it, and check the result — especially pages that were a very different shape (Legal is longer than Letter) — to confirm nothing important is lost at the edges. Padding never clips (it only adds space). After normalizing, verify a few pages, particularly any that changed shape significantly, before relying on the document.
Should I normalize before or after merging?: Either works; pick by convenience. You can resize each source PDF to the common size first and then merge (clean and predictable), or merge first and then resize the whole combined document to one size in one pass (fewer steps). Resizing-then-merging gives you control per source if they need different handling; merging-then-resizing is quicker when one uniform size suits everything. Both reach the same place: a merged PDF with consistent page sizes. For a simple "make it all Letter" job, merge then normalize the result; if sources need individual attention, resize each first. The order is a workflow preference, not a correctness issue.
What target size should I choose?: Match your audience and printing. In North America, Letter is the default; in most of the rest of the world, A4 — so choose the size your readers will print on, since printing a Letter-normalized PDF on A4 (or vice versa) reintroduces the scaling/cropping you were trying to avoid. Legal is unusual and rarely the right unifying target unless the content genuinely needs the extra length. So pick A4 or Letter by region/audience, normalize to it, and your merged document prints cleanly for the people who will print it. If the document is screen-only, the target matters less, but a consistent size still looks more professional.
Is it safe to do this with an online tool?: For confidential documents, prefer a tool that processes files locally. ScoutMyTool merges and resizes pages entirely in your browser tab, so your files never leave your machine. For anything sensitive, confirm the tool does not upload before using it — and check a few pages after normalizing to confirm nothing was clipped.

Citations

Wikipedia — “Paper size,” the dimensions involved. en.wikipedia.org/wiki/Paper_size
Wikipedia — “ISO 216,” the A4 paper standard. en.wikipedia.org/wiki/ISO_216
Wikipedia — “Letter (paper size),” the North American standard. en.wikipedia.org/wiki/Letter_(paper_size)

One clean document, whatever the sources

Merge mixed-size PDFs and normalize them to one size with ScoutMyTool’s in-browser tools — your files never leave your machine. Check the edges after resizing.

Open Merge PDF →