Merge PDF files
Join up to 20 PDF files into one document, in the order you choose. Your own browser reads and merges the files, so nothing is uploaded, there is no sign up and no watermark, and the merged file is ready to download when the progress bar ends.
Drop PDF files here or click to choose
Your files never leave your device
PDF files, up to 100 megabytes eachLimits: Up to 20 PDF files, 100 MB each and 150 MB together, with up to 500 pages in each file and in the result. Larger input is refused with a message.
Files to merge, in order
Merged PDF
- Files merged
- 0
- Pages
- 0
- File size
- 0
How to use the Merge PDF
- Drop your PDF files on the box above, or click it to choose them. Each file is checked as it arrives.
- Put the files in order with the Up and Down buttons, and remove any you do not need.
- If you like, type a document title and a file name in the settings.
- Choose Merge PDFs and wait for the progress bar to finish.
- Choose Download to save the merged file.
Worked example
Load the example to see a merge without a PDF of your own. The tool draws two small files in this tab, a two page A4 letter and a one page US Letter chart in landscape, and lists them in that order. Choose Merge PDFs and the result reads:
example-letter.pdf: 2 pages, A4 portrait example-chart.pdf: 1 page, US Letter landscape
- Files merged
- 2
- Pages
- 3
- File size
- 2.30 KB (2,360 bytes)
How to read the results
- The file list
- Each row shows a file's place in the merge, its page count and its size. A row that says why it cannot be used, such as a damaged file or one that needs a password, blocks the merge until you remove it or choose to skip it.
- Files merged
- How many files went into the result. When you choose to skip files that cannot be used, the note under the figures names the skipped ones.
- Pages
- The page count of the merged file, which is the sum of the pages of the files that were merged.
- File size
- The size of the merged PDF, rounded and then in exact bytes. It is the size of the file Download saves.
How this tool works and its limitations
The page loads no PDF code until you add a file or load the example. Then it downloads pdf-lib, an open source PDF library (the maintained @cantoo fork, about 250 KB compressed), shows the download as a progress bar, and runs it in a background worker so the page never freezes.
Each file is checked as it is added: the first 1,024 bytes must hold the %PDF- marker every PDF starts with, then the worker opens it to count its pages. A file that needs a password, or has only an owner password, is refused at this step, and the tool never tries to open it without its password.
The merge opens the files one at a time in list order, copies every page into a new document, points links between pages of the same file at their new pages, and saves the result. The new file gets no author, creator or dates, and a title only when you type one. The libraries this page uses are listed with their licenses on the open source licenses page.
- Bookmarks are not carried over: the merged file has no outline, because each file's bookmarks belong to that file alone.
- Form fields are flattened: each field's value becomes part of its page as it was drawn, and the field can no longer be filled in or changed. A field saved without a drawn appearance comes out empty.
- Document level JavaScript and the document's own title, author and dates are not copied; the title is set only when you type one.
- A digital signature in a source file does not stay valid, since it covers the bytes of the signed file and the merged file is a new one.
- Links that jump to a page named by a label rather than by its number, and links to other PDF files, may stop working.
- Accessibility tags of the source files are not carried over.
- Up to 20 files in one job, each up to 100 MB and 150 MB together, with up to 500 pages in each file and in the result; more is refused with a message.
Features
- Copies every page of every file in list order, keeping each page's size, orientation and rotation.
- Checks each file first and says which ones cannot be used and why.
- Runs in a background worker, so the page stays responsive, and Cancel stops a job at once.
- Keeps links to other pages of the same file pointing at the right page.
- Free, with no account, no watermark and no daily limit.
What a merge keeps and what it leaves out
A merge copies the pages themselves. The drawing instructions of each page, with its fonts and images, are copied as they are rather than redrawn, so text stays selectable and pictures keep their quality. What lives outside the pages does not come along: bookmarks and document level JavaScript are left out. Form fields are flattened, so each value filled in becomes part of its page and can no longer be edited, and the merged file looks the same in every reader.
Signed and protected files
A digital signature seals the exact bytes of the file that was signed, so no merged file can carry a valid one, whichever tool makes it. When a signature matters, send the signed file on its own. Files that need a password to open are refused with a message. So are files that open freely but carry an owner password limiting printing or copying, because a copy made here would quietly lose those limits. If you are allowed to, save an unprotected copy in a PDF reader and merge that.
Page sizes, order and file size
Every page keeps its own size, so an A4 letter followed by a US Letter chart stays a mix of the two; nothing is scaled to match. The order of the list is the order of the pages, file by file. The merged file comes out close to the sizes of the inputs added up, and a little smaller for small files, because the index at the end of a PDF is written in a compact form. A merge never compresses pictures, so for an upload form with a size limit, shrink photos with the Image Size Reducer before they become PDFs.
Frequently asked questions
How many PDFs can I merge at once?
Up to 20 files in one job, each up to 100 MB and 150 MB in total, with at most 500 pages in each file and in the result. To join more, merge them in groups and then merge the groups, as long as each result stays within 500 pages.
Are my files uploaded to a server?
No. The files are read inside this tab by a copy of pdf-lib that runs in your browser, and the merged PDF is made there too. The library is downloaded once, when you add the first file.
Why does the list say a file is password protected?
That file is encrypted with a password needed to open it, and the tool never asks for passwords. Open it in your PDF reader with the password, save a copy without protection, and add that copy instead.
Will the links inside my PDFs still work?
Web links work as before, and a link that jumps to another page of the same file is pointed at that page in the merged file. Links that use a named destination, or that open a different PDF file, can stop working, and bookmarks are not carried over.
Can I merge PDF forms and keep them fillable?
Not as a form. Each field is flattened: the value it holds becomes part of the page, so it reads the same in every reader but can no longer be changed. Keep the original file if you will need to edit the form again.
Does merging lower the quality of my pages?
No. Pages are copied with their own fonts, pictures and drawing instructions, not turned into images, so a scanned page stays as sharp as it was and typed text stays searchable.
Last updated .