Join two or more PDFs into one, in the order you choose
The tool loads here. It needs JavaScript, because the work happens on your device.
Your files and your privacy
Your PDFs are never uploaded. Each file is read into this browser tab, merged by a Web
Worker running on your own device, and handed back as a download. The page's
Content-Security-Policy restricts connect-src to this origin, so the browser itself would
block an upload even if the code attempted one.
What this tool does
Combine several PDF files into a single document without uploading them. Files are read
into this browser tab, joined in the order you listed them, and offered back as one PDF
you download.
Merging copies every page of every file you choose into one new document, in the order the
list shows, and writes that document out as a fresh PDF. Page content, page size and page
rotation are carried across unchanged, so a mixed set of A4 and US Letter pages stays
mixed rather than being stretched to one size. The output is a new file; your originals
are untouched.
How to use it
Select Choose PDF files and pick two or more PDFs from your device.
Check the list: files are merged top to bottom, and the page count and size of each one
is shown so you can confirm you picked the right documents.
Select Run. A progress bar reports each file as it is copied in.
Select Download to save the combined PDF, then Clear files and free memory when you are
finished.
Example use cases
Putting a signed contract, its appendix and a scanned ID page into one file before
emailing it.
Combining monthly bank statements into a single document for an accountant.
Joining separately scanned chapters back into one manuscript.
Assembling a portfolio from several exported design files without installing anything.
Supported input and output
Accepts
PDF (application/pdf), two or more files, up to 50 MB each
Unencrypted documents only
Produces
A single PDF, named merged.pdf
What this tool will not do
It will not open a password-protected PDF. Encryption is reported, never bypassed:
unlock the file in the application that produced it first.
Bookmarks, form fields, annotations and attachments are not carried across. Only page
content is copied, which is what pdf-lib's page copying preserves.
A digital signature on any input is invalidated, because the output is a new document.
That is true of every PDF editor, not just this one.
Files are merged in the order you selected them; there is no drag-to-reorder on this
page. Use Reorder pages in the toolkit if you need to rearrange afterwards.
Very large sets are limited by your device's memory, because the work happens on your
device. 50 MB per file is the accepted maximum.
Common mistakes
Choosing one file and expecting a result: merging needs at least two, and a single file
is rejected rather than silently copied.
Assuming the merged file will be smaller. Merging adds pages, so the output is roughly
the sum of the inputs; this tool does not compress.
Expecting the table of contents to survive. Bookmarks are dropped, so a merged manual
needs its contents rebuilt elsewhere.
Closing the tab before downloading. Nothing is stored anywhere, so an undownloaded
result is gone.
Technical notes
Merging is done with pdf-lib inside a Web Worker, so a large document does not freeze the
page. Each source file is parsed, its page indices are copied into a newly created
document, and the result is serialised once at the end. The worker is terminated and its
buffers released when you select Clear files, rather than being left holding your document
for the life of the tab.
Frequently asked questions
Are my PDFs uploaded to a server?
No. There is no upload endpoint. The merge runs in a Web Worker in this tab, and the
page's Content-Security-Policy limits connect-src to this origin. You can confirm it by
opening your browser's network panel and running a merge: no request carrying document
bytes is made.
Is there a file size or page limit?
Each file may be up to 50 MB. There is no page limit beyond what your device's memory
allows, because the merging happens on your device rather than on a server.
Can I change the order of the files?
Files are merged in the order you selected them. To rearrange pages after merging, run
the combined file through Reorder pages, which shows every page as a thumbnail.
Why does my merged file still say it is not signed?
A digital signature covers the exact bytes of the document it was applied to. Merging
produces a new document, so any signature no longer matches and is dropped. Sign the
merged file after merging, not before.
Does the result carry a watermark?
No. The output is the pages of your inputs and nothing else. If you want a watermark,
the toolkit has a separate tool that adds one deliberately.