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Merge PDF

Combine several PDFs into one file in the order you choose, without leaving your browser.

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Quick answer

Merge PDF joins two or more PDFs into a single document using pdf-lib, in your browser. It copies every page of each file, in the order you list them, into one new PDF called merged.pdf. Your files are not uploaded, the originals are left untouched, and the only page cap is your device's memory.

  • 2+PDFs per merge
  • Losslesspages are copied
  • 1output file: merged.pdf
  • 0files uploaded

What the Merge PDF does

Typical cases: a report whose sections arrived as separate exports, a scanned contract plus its signed signature page, or three invoices a client wants as one attachment. Merge PDF joins them end to end so you send, print or file one document instead of a folder of pieces.

It works page by page. Every page of every file you add is copied whole into a fresh PDF, so text stays selectable and links keep working. Your source files on disk are not modified; the tool writes a new merged.pdf.

How it works

When you drop in two or more PDFs, the browser reads each one into memory and passes it to pdf-lib, an open-source library that creates and edits PDFs in JavaScript. No plugin, server or copy of Acrobat is involved.

pdf-lib opens each source document and copies its pages, with their content, fonts and embedded images, into a new document, appending them in the order your files are listed. After the last file's pages are in place it writes out a single PDF and your download starts.

Processing pipeline

  1. Step 1. Add two or more PDFs by dragging them in or picking them. They are read from your device.
  2. Step 2. Arrange the files. They merge top to bottom in the order shown, so reorder before you run it.
  3. Step 3. pdf-lib creates an empty document and copies every page from each file into it, one file after another.
  4. Step 4. The combined PDF is written in memory and offered as a single download, merged.pdf.
  5. Step 5. Your original files stay as they were. Only the new merged copy is created.

Pages keep the order you set

File 1123File 212merged.pdf12345pages 1–3 from File 1,pages 4–5 from File 2
Example: a 3-page file followed by a 2-page file gives a 5-page merged.pdf. Pages are copied rather than re-rendered, so they keep their quality.

Privacy

Your PDFs stay on your device. They are read from disk, merged in the page's memory, and the combined file is generated locally, so NineClip never receives a copy.

Nothing is kept after you close the tab, and the tool needs no login. That makes it suitable for contracts, financial statements, medical records and anything else you would not upload to someone else's server.

Technical details

Enginepdf-lib (open-source, JavaScript)
InputTwo or more PDF files
OutputOne merged PDF (merged.pdf)
OrderUpload order, top to bottom
QualityLossless: pages are copied, not re-rendered
UploadNone; the merge runs in your browser
LimitYour device's memory, on very large sets

Standards and references

  • ISO 32000 (PDF): the PDF specification. Merging works on the page tree it defines: each page is an object that can be copied between documents without being re-rendered.
  • pdf-lib: the open-source JavaScript library that builds the new document and copies pages across, with no server or native code.

Accuracy and limits

Pages are copied rather than reprinted, so text stays sharp and selectable, images keep their resolution, and the result is roughly the size of its parts added together. Merging is lossless.

Everything happens in memory, so a very large batch (dozens of files, or a few that run to hundreds of megabytes) can be slow or run out of memory on a phone or an older laptop. If a merge stalls, combine the files in smaller groups.

Pages arrive intact and in order, but the bookmarks (the outline sidebar) from the separate files are not rebuilt into one combined tree.

Real-world uses

One report from many exports

Stitch separately exported chapters, a cover page, and an appendix into a single deliverable.

Contracts and signatures

Append a signed signature page or an addendum to the original agreement so the whole thing is one file.

Scans into one record

Combine pages scanned in separate passes (front and back, or a stack fed in batches) into one document.

Submission bundles

Merge invoices, receipts, or forms into the single PDF a portal or client asked for.

When it fits, and when it doesn't

Good for

  • Joining whole PDFs end to end
  • Keeping text, links and image quality intact
  • Private or sensitive documents
  • Building one file to submit or archive

Not the best choice for

  • Picking only some pages from a file
  • Reordering or deleting pages within a file
  • Carrying bookmarks into one combined outline
  • Reducing the size of the combined file

To pull specific pages before merging, use Split / Extract PDF Pages. To drop pages, use Delete PDF Pages. To shrink the result, try Compress PDF.

Tips and tricks

What we would do

Frequently asked questions

Does merging upload my files anywhere?
No. pdf-lib reads and combines every file inside your browser. Nothing goes to a server, and refreshing the page clears it all from memory.
What order do the PDFs end up in?
The order they are listed in before you run it: top file first, bottom file last. Arrange them the way you want the final document to read, then merge.
Will merging reduce quality?
No. Pages are copied whole, not re-rendered or recompressed, so text stays selectable and images keep their original resolution. The process is lossless.
How many PDFs can I combine at once?
There is no fixed cap. Everything is held in the browser, so the practical limit is your device's memory. Very large batches go better in smaller groups.
Can I merge only certain pages from a file?
Not in this tool, which joins whole files. To take just pages 1-3 of one PDF, run it through Split / Extract PDF Pages first, then merge the result.
Does the merged file keep bookmarks and the table of contents?
Page content, text and links carry over. The bookmark outlines from the separate files are not rebuilt into one combined sidebar, though every page is present and in order.
Are my original files changed?
No. The tool builds a new file called merged.pdf and leaves your source PDFs on disk exactly as they were.
Can I merge password-protected PDFs?
Not while they are locked. pdf-lib has to read each page, so remove the password first (with an unlock tool, for example), then merge the unlocked copies.
Can I combine PDFs with different page sizes?
Yes. Each page keeps its own dimensions, so a mix of A4, Letter and scanned-receipt pages all sit together in one file at their original sizes.
Does it work on my phone?
Yes. It runs in any modern mobile browser just as it does on a desktop, though very large files are more likely to strain a phone's memory.
Is there a watermark or a file limit?
There is no watermark and no daily limit. You can merge as often as you like.

References

Checked line by line against the tool's pdf-lib merge code, including the fact that bookmarks from the source files are not merged.

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Back to the Merge PDF

Your file is processed on this device and never uploaded, and there's no account to create.

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