Does merging change the page size or orientation of my original PDFs?

No -- each file's own pages keep their original size and orientation exactly as they were. Merging only combines the files into one document in the order you choose; it doesn't resize, rotate, or reformat any page.

Is there a limit to how many PDFs I can merge at once?

There's no fixed limit on the number of files -- you can add as many as you need and reorder them before merging. The practical limit is your device's own memory for very large batches, since everything processes in your browser.

Will this work on a password-protected PDF?

No, honestly -- a PDF that needs a password to open will fail to merge, with a generic error rather than a special message explaining why. Remove the password first (most PDF viewers, including free ones, can do this if you know the password) and then merge the unlocked version.

Are my files actually uploaded anywhere?

No -- merging runs entirely in your browser using your device's own processing power. Your PDFs never leave your device, there's no server upload involved, and nothing about their contents is visible to us at any point.

Can I merge files with different page sizes, like some Letter and some A4?

Yes -- each page keeps its own original size in the merged document. The result is one PDF where different pages can genuinely be different sizes, which is completely normal and how the original files looked; merging doesn't force everything onto a single uniform page size.

Will merging a lot of large PDFs on my phone cause it to freeze or crash?

It's possible with a large enough batch -- since everything processes using your device's own memory, a phone merging many large files (dozens of pages each, several files) has less headroom than a laptop. If you hit this, try merging in smaller batches (a few files at a time, then merge those results together) rather than everything at once.

I added the same file twice by accident -- do I need to start over?

No -- you'll see a warning if a duplicate is detected, but it won't block you. Just remove the extra copy from the list using its own remove button, then continue reordering and merging normally.

What's the difference between this and Organize PDF?

Merge PDF combines separate files into one document -- its whole job is taking multiple PDFs and producing a single new one. Organize PDF works on pages within a single PDF you already have -- reordering, deleting, or rotating individual pages using real page previews. If you need to combine files, use Merge; if you need to fix the page order or remove a page inside one PDF you already have, use Organize (there's a direct link to it after merging).

Home/PDF Tools/Merge PDF

Merge PDF

Combine multiple PDF files into one document

Files never stored

Drop PDF files here or click to browse

Select multiple PDF files to merge them into one

Works with any file size -- files over 50MB may just take a little longer

What this tool does

A tool for combining two or more PDF files into a single document, in whatever order you choose. This is the everyday fix for the common situation where you've scanned several pages separately, or received a contract as multiple attachments, and need them as one file to send or print. Drop your PDF files into the upload area (or select them one at a time), then drag to reorder them into the sequence you want -- or use the up/down arrow buttons on each file if you'd rather not drag. Once the order looks right, click merge and download the combined file. The merge happens entirely in your browser, so nothing is uploaded to a server in the process.

Pro tips

If you're merging a scanned document with a typed cover letter, merge them in the order a reader would expect to see them — cover letter first, then the scanned pages. Adding the same file twice by accident shows a warning, but doesn't block you -- remove the duplicate from the list if it wasn't intended.

Continue with

Compress PDF

Keep the combined file small enough to share easily

Organize PDF

Drag pages into the right order

Watch: Merge PDF in Action

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Plays on YouTube (counts toward our @freedailypro channel).

Frequently asked questions

How to use Merge PDF

Start by dropping every PDF you want combined into the upload area -- you can select them all at once from a file picker, or drag them in one at a time as you gather them. Once they're loaded, each file shows as its own card in a list. Drag any card up or down to change where it lands in the final document, or use the small up/down arrow buttons on each card if you'd rather click than drag (useful on a touchpad, or if you're merging a long list and don't want to scroll while dragging). There's no limit on how many files you can combine in one pass, though very large batches (dozens of files, or files that are individually hundreds of pages) will take longer to process since your browser is doing all the actual PDF manipulation itself.

Once the order looks right, click Merge. The tool reads every page from every file, in the order you set, and assembles them into one new PDF -- it doesn't touch or modify your original files, it builds a fresh document from copies of their pages. When it's done, a Download button appears with the combined file, named automatically based on your first file's name (you can rename it after downloading, same as any other file).

When to use it

The most common real use is combining a scanned cover page or signature page with the rest of a document -- for instance, you print, sign, and scan just the signature page of a contract, and need to reattach it to the original multi-page PDF rather than resending the whole thing as two separate attachments. It's also useful for combining multiple scanned pages that came in as separate files from a scanner or scanning app, assembling a portfolio or report from several source documents (a cover letter PDF plus a resume PDF plus a writing sample PDF, for example), or consolidating a set of invoices or receipts into one file for an expense report.

When not to use it

If you need to combine specific page ranges from different documents rather than whole files (say, pages 2-4 from one PDF and page 1 from another), merge this tool with Split PDF first -- split out just the pages you need from each source, then merge those extracted pieces together. If your goal is actually to compress a large merged file for emailing, run Compress PDF as a second step after merging, since merging itself doesn't reduce file size.

Tips for best results

If two source PDFs use noticeably different page sizes (a US Letter document merged with an A4 one, for example), the resulting file keeps each page at its own original size rather than forcing everything to match -- this is usually fine for on-screen viewing but worth knowing if the merged file is going to print, since page sizes will visibly differ between sections. For a merge you'll need to repeat regularly with the same file names (a monthly report built from the same three source documents, say), keep those source files named consistently so it's quick to spot and re-upload the right ones each time rather than hunting through a folder.

Limitations

Password-protected or encrypted PDFs can't be merged directly -- remove the password first (there's a dedicated tool for that) before combining. Very large files (hundreds of megabytes) may process slowly or use a noticeable amount of your browser's memory, since the whole operation runs in your browser tab rather than on a server; if a merge seems to hang, it's often still working on a genuinely large batch rather than stuck.

Privacy

The merge itself runs entirely inside your browser using a PDF-manipulation library loaded once when you open the page -- your files are read directly from your device's memory and the combined result is generated the same way, with no upload to any server at any point in the process. Closing the tab clears everything; nothing persists after you leave the page.