Merge PDF

Combine several PDFs into one document, in your order. Free, no upload. 1 GB max · Up to 1 GB · Processed locally, never sent to a server.

A complete pack rarely arrives as a single document. The quote comes out of the invoicing software, the terms and conditions from a saved template, the annexes from the office scanner, the certificate from a government portal. Merge PDF assembles those pieces into one document, and the order it uses is exactly the order of the list shown on screen just before you start.

The mechanics are direct. The pdf-lib library is loaded, an empty document is created, then every page of every file is copied into it, one after another. Nothing is re-encoded, nothing is resized, no page is cropped. The result is always called fusion-nexavo.pdf and carries a note with the number of files assembled.

A classic online service asks you to upload six documents before handing back a link. Here, the only thing that crosses the network is the pdf-lib library itself, served from the site’s own assets folder the moment you start the assembly: code comes down, no papers go up. For a law firm, an HR department or a practice handling documents covered by professional confidentiality, that distinction is not cosmetic.

How to use it

  1. Drop in at least two PDFs With a single file the run stops on a message asking you to add at least two PDFs to merge. Files added later are placed at the end of the list.
  2. Check the order on screen The list follows the order in which the system handed the files over, which is not always the alphabetical order of your folder. This is the moment to check it.
  3. Reorder with the arrows Every row carries an up arrow, a down arrow and a cross. The arrows swap a file with its immediate neighbour; the cross drops it from the merge.
  4. Click Run The progress line names the file being added, so you can see straight away which one is at fault if the run stops on a read error.
  5. Collect fusion-nexavo.pdf The output name is fixed. Rename it at download time to match your own convention, then check the total page count of the document you got.

The assembly order, in detail

The merge is sequential and complete: every page of the first file, then every page of the second, and so on to the last. There is no interleaving and no page selection at this stage. If you only want pages 2 to 5 of an annex, pull them out first with Split PDF, then merge the file you get with the rest of the pack.

Each page keeps its original dimensions and its original rotation. A finished document can therefore alternate A4 portrait, A4 landscape and A3 without anything being adjusted. That is usually what you want, since a wide table stays readable, but it does surprise people at print time: remember the fit-to-page option in the print dialog.

The files the merge turns away

pdf-lib is called with ignoreEncryption set to false. Any encrypted document is therefore rejected, whether it asks for a password on opening or merely forbids printing and copying. The error message names the offending file in quotes and mentions both possible causes: a damaged document, or password protection.

That detail matters when you are assembling eight items, because it saves you testing them one by one. The protection then has to be removed in the software that produced the document, before you run the merge again. A file truncated by an interrupted download triggers the same error; in that case, fetch it again.

What the merged document does not inherit

The destination document is created empty, and only pages are copied into it, with their content, their fonts and their images. Everything that lives at document level stays behind: bookmarks and the navigation outline, title and author metadata, any attachments. Interactive form fields do not survive this kind of copy reliably; if your documents contain them, open the result and test them before sending it.

Another consequence of the method: shared resources are not pooled. Ten reports that embed the same font still embed it ten times after assembly, and the finished document weighs roughly the sum of the files you started from. A pass through Compress PDF after the merge settles that question.

When merging is not the right answer

The file picker only lets the application/pdf type and the .pdf extension through. To bring in photographs or screenshots, go through JPG → PDF; for a report still in your word processor, through Word → PDF; then merge the PDFs you obtain.

Finally, if the pack has to be signed, merge first and sign afterwards with Sign PDF. Do it the other way round and the signed page risks ending up in the middle of the document rather than at the end.

Frequently asked questions

In what order are the files assembled?

Top to bottom of the list shown before you start, with no automatic sorting of any kind. Each click on an arrow moves a file by one position, and files added along the way stack up at the end.

Can I merge documents of different page sizes?

Yes. Each page keeps its size and its orientation: an A3 landscape sheet sits alongside A4 portrait pages without any trouble.

The merge fails and names one of my files. What now?

That document is encrypted or corrupted. The library refuses to read a protected PDF, even when the protection only covers printing. Remove the password, then run the merge again.

Are the bookmarks from my documents carried over?

No. The final file starts from an empty document into which only pages are copied: navigation outline, bookmarks, metadata and attachments from the sources are not transferred.

Why does the result weigh as much as the sum of the originals?

Because no recompression takes place and identical resources are not deduplicated. That weight is expected; follow up with Compress PDF if the file has to go out by email.

How many files can I assemble at once?

No ceiling is written into the code, but every document is opened in memory before assembly, so the real limit is your device. Each individual file is still capped at 1 GB.

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