Merge PDF

About this tool

This free Merge PDF tool combines several PDF files into a single document, in the order you add them — chapters into a report, scanned pages into one file, a contract and its appendices into one attachment.

Everything runs in your browser — your files are never uploaded to a server. There is no file size cap, no page limit, no watermark and no account.

Why the "nothing uploaded" part matters here

Of all the file types people convert online, PDFs are the ones most likely to contain something they would not want on a stranger's server.

Think about what actually gets merged: signed contracts, bank statements, medical letters, passport scans for a visa application, tax returns, payslips, tenancy agreements, invoices with client details. Every one of those goes into a normal online PDF tool as an upload to a machine you know nothing about, kept for a retention period you were never told.

This tool never sends the file anywhere. Your browser reads each PDF, builds the combined document and hands it back, all on your own computer. You can verify it: load the page, disconnect from the internet, and merge. It still works.

That also explains the limits. If something goes wrong we cannot look at your file, and we cannot recover it — we never had it.

What merging actually does to your file

A PDF is a container of page objects plus the resources those pages point at — fonts, images, colour profiles. Merging rebuilds a new container holding all the pages from all the input files in sequence, carrying their resources with them.

What comes through intact:

• Every page, at its original size and resolution — nothing is re-rendered or re-compressed
• Embedded fonts, images and vector graphics
• Text, so the result stays searchable and selectable if the sources were
• Different page sizes and orientations, which simply sit next to each other in the output

What may not survive:

• Form fields — two files with fields of the same name can conflict, and interactive forms often flatten
• Digital signatures — these sign a specific document, so combining invalidates them. This is by design, not a bug.
• Bookmarks and outlines — often lost or partially kept
• Annotations and comments — usually preserved, occasionally not
• Attachments embedded in a PDF — frequently dropped

For an ordinary report, scan or contract none of this matters. For a filled-in form or a signed document, check the result before you rely on it.

Getting the order right

Pages appear in the order the files are added, so the order you add them is the order you get.

Two things that trip people up:

Dragging several files at once does not guarantee order. Browsers do not always hand over a multiple selection in the order you see on screen. If sequence matters, add the files one at a time, or name them so the order is unambiguous.

Name files with zero-padded numbers. page-1, page-2 … page-10 sorts as 1, 10, 2 in almost every system. page-01, page-02 … page-10 sorts correctly everywhere. This is worth fixing at the scanner, since it is the single commonest cause of a merged document coming out shuffled.

If you only need part of a file, split it first and merge the piece you want.

Page sizes that do not match

Merging does not resize anything. An A4 report combined with a US Letter invoice and a scanned receipt produces one PDF containing three different page sizes.

On screen this is barely noticeable — the viewer just fits each page to the window. In print it is obvious, as pages shift and margins jump around.

If everything must match, the reliable route is to make the sizes agree before merging: open each file, print to PDF at the target paper size, then merge. Most print dialogues offer a "fit to page" option that handles the scaling.

Mixed orientation behaves the same way. A landscape spreadsheet among portrait pages stays landscape, which is usually what you want for a wide table.

How to use it

• Add PDFs — click the upload area or drag and drop two or more PDF files
• Merge — click the button to combine them in order
• Download — save your merged PDF

Good to know

• Password-protected PDFs will not merge. Remove the password first with Unlock PDF, then combine.
• The merged file is roughly the sum of the inputs. Merging does not compress; run Compress PDF afterwards if the result is too large to email.
• Very large jobs depend on your device's memory, since everything happens locally. A few hundred pages is fine on a laptop; the same job may struggle on an old phone.
• Signatures break. A digital signature covers one exact document, so merging necessarily invalidates it.
• Check a filled form afterwards. Field values can be lost when two documents define the same field name.
• Scanned pages stay images. Merging does not add searchable text; run Image to Text if you need that.

Common questions

Are my PDF files uploaded to a server?

No. The entire merge happens inside your browser on your own device — nothing is transmitted and nothing is stored. You can confirm it by loading the page, disconnecting from the internet, and merging anyway. This matters because merged PDFs are so often contracts, statements, medical letters and scanned identity documents.

Is there a limit on file size or number of pages?

None imposed by us. Because there is no server paying for the work, there is nothing to cap. The practical limit is your own device's memory: a few hundred pages is comfortable on a normal laptop, while a very large job on an old phone may run out of room.

Can I change the order of the pages?

The files are merged in the order you add them, so add them in the order you want. If sequence matters, add them one at a time rather than selecting several together, as browsers do not always pass a multiple selection in the order shown. Naming files with zero-padded numbers — 01, 02, 10 — keeps them sorting correctly everywhere.

Why won't my PDF merge?

The usual cause is a password. An encrypted PDF cannot be read without being unlocked first, so remove the protection and try again. The other causes are a corrupt file, or a .pdf that is not really a PDF — some scanners and email systems produce files with the wrong extension.

Will merging reduce the quality of my pages?

No. Pages are copied as they are, not re-rendered or re-compressed, so text stays sharp and images keep their original resolution. The output is therefore about as large as the inputs added together. If you need it smaller, compress it as a separate step afterwards.

Does merging keep my form fields and signatures?

Form fields often survive but can conflict when two documents use the same field name, and interactive forms may flatten. Digital signatures are always invalidated, because a signature applies to one exact document and merging creates a different one. Always check a filled form or a signed file after combining.

Will the merged file keep different page sizes?

Yes. Nothing is resized, so an A4 document merged with a US Letter one produces a PDF containing both sizes. It looks fine on screen but shows up when printed. To make them match, print each file to PDF at your target paper size first, then merge.

Related tools

• Split PDF — take out the pages you want before combining
• Compress PDF — shrink the merged file so it will send by email
• Unlock PDF — remove a password so a file can be merged
• Organize PDF — reorder, rotate and delete pages in the result