DDanfio

Merge PDF

Most "free" PDF mergers work by uploading your file to somebody else's server, processing it there and hoping the copy is deleted afterwards. A contract, a payslip, a medical letter or a passport scan all pass through that machine in the process, which is why the privacy question matters more here than it does on a mortgage calculator.

Drag & drop files here, or .

Everything is processed in your browser - nothing is uploaded.

    Two or more PDFs: up to 20 files, 25 MB each and 80 MB for the whole job.

    Saved to your device as this name with .pdf added.

    Results update as you type. Nothing leaves your device.

    Output file

    merged.pdf

    Add your PDFs above and they are joined in the order you add them, keeping every page exactly as it is.

    Merge order
    As added
    Files per job
    up to 20
    Per-file limit
    25 MB
    Job limit
    80 MB

    What happens when you add files

    1. Each PDF is opened on this device and its page count is read - no upload, no queue, no email address.
    2. Pages are copied into one new document in the order you added the files, carrying each input's fonts and images into the single output.
    3. A download button appears for merged.pdf, with a table showing how many pages each input contributed.

    What the merge preserves

    FeatureKept in the output?
    Page order inside each fileYes, unchanged
    Page size and orientationYes, per page
    Text, so it stays searchableYes
    Bookmarks, form fields and digital signaturesNo: only the page content is copied
    Structure tags used by screen readersNo: the output is untagged
    Password protectionNot carried over: unprotected files only

    A merged file keeps the pages, not the paperwork. Document-level features live outside the pages themselves, so bookmarks, fillable fields, signature fields and accessibility tags do not survive the copy.

    Password-protected PDFs are refused rather than guessed at. This tool runs inside your browser and never sees your files, so it has nowhere to type a password: open the file once, save an unprotected copy, then merge that.

    This merger runs inside the browser tab. Your files are read with the file-picker API, the pages are copied from one document into another on your own device, and the finished PDF is handed to you as a download. Nothing is uploaded, there is no queue, no account and no watermark.

    How this merge pdf works

    How a PDF merge actually works

    A PDF is a container of numbered objects: pages, fonts, images and streams of instructions, tied together by a page tree and a cross-reference table. Merging does not re-render anything. It reads the page tree of each input, copies the page objects and the resources they point at into a new document, and writes a new cross-reference table for the result.

    That is why a merge is fast and lossless: the text stays text, so the merged file is still searchable, the vector content stays sharp at any zoom level, and page size and orientation are copied per page rather than forced into a single size. It is also why the merged file can be larger than the inputs added together - each input brings its own fonts and images along, and nothing is deduplicated between them.

    The copy happens in JavaScript on your device using pdf-lib, an open-source PDF library. A 20-page merge is usually a fraction of a second; the limiting factor is reading the files off disk, not the page copying.

    What survives a merge, and what does not

    Everything that lives inside a page survives: the text, the images, the vector drawings, links drawn as annotations on the page, and the page geometry. That covers the vast majority of what people merge.

    Features that live at document level do not come along, because they sit in the catalogue of the original file rather than on its pages: bookmarks and outlines, AcroForm fields, signature fields, layer visibility settings, and the structure tags that screen readers follow. A merged file is therefore untagged, and a signed document that is merged stops being a verifiable signed document - the visible signature is copied as page content, but the cryptographic proof is not.

    Password-protected PDFs cannot be merged here. The library refuses an encrypted document rather than guessing at it, and since the file never reaches a server there is nowhere to type a password. Open the file once in a reader that has the password, save an unprotected copy, and merge that.

    Order, naming and the limits worth knowing

    The order of pages in the output follows the order of the files you added, so the act of dropping them in is the act of arranging them. If you would rather not worry about the order you drop them in, switch the merge order to alphabetical by file name, which sorts natural numbers sensibly - appendix 2 comes before appendix 10 rather than after it.

    The output is saved to your device as the name you type with .pdf added. Rename it before you start if the file is heading into a shared folder or an upload form with a filename rule.

    This page accepts up to 20 files per job, 25 MB per file and 80 MB in total, because everything is held in memory in the tab. Documents beyond that size are better merged one pair at a time, which also keeps each download small enough to check as you go.

    Worked examples

    Each example below was run through the calculator on this page when the site was built, so the numbers match what you see when you enter the same inputs.

    Two quarterly reports into one file

    Merge order
    In the order I add them
    Output file name
    2026-q3-financials

    Output file

    2026-q3-financials.pdf

    Add your PDFs above and they are joined in the order you add them, keeping every page exactly as it is.

    Merge order
    As added
    Files per job
    up to 20
    Per-file limit
    25 MB
    Job limit
    80 MB

    Adding the March report (12 pages) and then the June report (8 pages) gives a 20-page 2026-q3-financials.pdf, with March on pages 1-12 and June on pages 13-20.

    Chapters merged in alphabetical order

    Merge order
    Alphabetical by file name (A to Z)
    Output file name
    handbook

    Output file

    handbook.pdf

    Add your PDFs above and they are joined in alphabetical order by file name, keeping every page exactly as it is.

    Merge order
    A to Z
    Files per job
    up to 20
    Per-file limit
    25 MB
    Job limit
    80 MB

    Chapters named 01-intro.pdf through 09-appendix.pdf land in that order without any dragging, so handbook.pdf starts with chapter 1 even if the last file was added first.

    A contract plus its signed scan

    Merge order
    In the order I add them
    Output file name
    contract-signed

    Output file

    contract-signed.pdf

    Add your PDFs above and they are joined in the order you add them, keeping every page exactly as it is.

    Merge order
    As added
    Files per job
    up to 20
    Per-file limit
    25 MB
    Job limit
    80 MB

    A 4-page contract followed by a 2-page scan of the signed page gives a 6-page contract-signed.pdf. The signature is visible on page 6, but the digital signature that proved who signed it does not travel into the copy.

    Frequently asked questions

    Is this PDF merger really free, with no account and no watermark?

    Yes. There is no sign-up, no email step, no page limit and nothing stamped on the output. The job runs in your own browser, so there is no server cost to recover and no reason to hold anything back. The limits that do exist are technical: 20 files per job, 25 MB per file and 80 MB in total, because every page is held in the tab memory while the merge runs.

    Are my PDFs uploaded to a server?

    No. The file picker and drag-and-drop handler read the files through the browser APIs, pdf-lib copies the pages in memory in the page you are looking at, and the download is created from a Blob URL that exists only in the tab. There is no upload endpoint involved, which you can confirm by watching the network panel of your browser developer tools while you merge, or by going offline and merging anyway.

    Can I merge a password-protected PDF?

    Not directly. An encrypted document is refused with a message rather than half-merged, and because the file never leaves your device there is nowhere for this page to ask for the password. Open the file once in a reader that knows the password, choose to save or print a copy without protection, and merge that copy instead.

    Does merging reduce quality or change the file size?

    Quality is untouched: merging copies pages as they are, with no re-rendering and no recompression, so text stays text, images keep their original resolution and vector art stays sharp. The size of the merged file is usually close to the sum of the inputs, and can be a little larger because nothing is deduplicated between files - if two inputs embed the same font, the merged document carries both copies.

    Why do bookmarks, form fields and signatures disappear after merging?

    Because they are stored once for the whole document rather than on a page. A PDF keeps its outline, its fillable fields, its signature fields and its accessibility tags in the document catalogue, while a merge copies page objects. Filling form fields before merging keeps the answers visible as page content; if working fields are essential, fill the merged file afterwards in a PDF editor rather than before.

    Can I reorder pages or pull a few pages out while merging?

    Merge joins whole documents, so order comes from the order of the files. If you need a subset in a particular sequence, split the pages you want first and merge those outputs, or use a page-organising tool to arrange them. Both routes keep the originals untouched, so nothing is lost by experimenting.

    Assumptions and sources

    • Processing: pdf-lib (MIT licensed) runs in your browser. Pages are copied object by object, so text stays selectable and searchable and no page is re-rendered or recompressed.
    • Limits: 20 files per job, 25 MB per file and 80 MB in total, all held in the browser tab while the merge runs.
    • Not preserved: outlines and bookmarks, AcroForm fields, signature fields and structure tags, because those live in the document catalogue rather than on the pages.
    • Privacy: no file, file name or page content is sent to danfio.com. There is no upload endpoint behind this tool, and the download is a Blob held in your own tab.

    Last reviewed 2026-09-14. This page is an estimate tool, not financial, tax or legal advice.Read the full disclaimer.

    Related tools

    Split PDFPDF & DocumentsSplit a PDF in your browser: pull page ranges out into separate files or one file, or cut the document every N pages. No upload, no account, no watermark.Open calculator →Invoice GeneratorBusiness & FreelanceCreate an invoice with line items, discounts, tax, deposits and late fees, then print it or save it as a PDF. Nothing is uploaded.Open calculator →Estimate GeneratorBusiness & FreelanceBuild a quote from materials, labour, contingency, overhead and markup, see the margin, and split the total into a deposit and progress payments.Open calculator →Timesheet CalculatorBusiness & FreelanceTurn daily hours into weekly pay with the 40-hour overtime rule, a daily overtime rule for states that use one, punch rounding and billable time.Open calculator →Merge PDFMerge PDF files in your browser: drag two or more PDFs in, keep every page in order and download one combined file. No upload, no account, no watermark.Open calculator →