Merge PDF
Drop PDFs, put them in order, get one file.
Drag the thumbnails to set the order — pages are joined in this order.
- 100% freeNo account, no daily quota, no paid tier.
- Nothing is uploadedFiles are processed on your device and never reach a server.
- No catch on the outputNo watermark, no forced downscaling, no size cap.
- Updated in the openEvery fix and every new tool is written down on the changelog page.
What this PDF merger does
Drop two or more PDF files, arrange them in the order you want with the arrow buttons, and click Merge. The pages of every document are copied into a single new PDF that keeps the original page sizes, orientation, text, links and images — a scanned contract followed by a typed appendix followed by an invoice comes out as one document with the pages exactly as they were. Each file in the list shows its page count and a thumbnail of its first page, so you can check you have the right version before you combine.
Everything runs in your browser using pdf-lib, an open-source PDF library. Nothing is uploaded, so there is no queue, no 'processing' wait on a remote server, no file size cap, no watermark and no account. A 200 MB set of scanned drawings merges as readily as three one-page letters — the only limit is your device's memory. The page also keeps working offline once loaded.
How to use it
Drag your PDFs onto the drop zone or click it to browse; you can also paste files copied from a folder. The list shows each file with its page count. Use ↑ and ↓ to reorder, × to remove one you added by mistake, and add more files at any time — they append to the end. When the order is right, click Merge; a progress bar runs while pages are copied, and the merged file appears in the results with its total page count and size. Click Download to save it.
The result can be handed straight to the next tool without re-selecting it: split it into new sections, or convert its pages to images for a slide deck or a preview. If you need to add photos or scans that are still JPG or PNG files, run them through the image-to-PDF converter first, then merge the result here. A password-protected PDF is refused — remove the password with Unlock PDF first; to lock the merged result, use Protect PDF.
Common pitfalls
Password-protected PDFs cannot be merged until they are unlocked — the tool ignores the weak 'permissions' password that only restricts printing or copying, but files that require a password to open must be decrypted in the application that created them. Form fields (AcroForms) are copied as static page content, not as live fields, so a merged tax form will no longer be fillable; the same applies to embedded JavaScript and some attachments.
Bookmarks (the outline in the sidebar) are not carried across from the source files, because each document's outline points into its own page tree. Merging does not compress anything: the output is roughly the sum of the inputs. If the result is too large to email, the culprit is almost always scanned pages stored as full-resolution images — convert them to images, compress them and rebuild the PDF, or ask the sender for a text-based version. Finally, order matters: check the thumbnails before merging, since the merged file cannot be un-merged (though you can split it again).
Background: how PDF merging works
A PDF is a tree of objects — pages, fonts, images, colour spaces — referenced by number from a cross-reference table at the end of the file. Merging is not a matter of concatenating bytes; each page's object, and every resource it references, has to be copied into the new document and renumbered so references stay valid. Fonts and images that two pages share inside one source file are copied once; the same font in two different source files is copied twice, which is why merged files can be slightly larger than the sum of their parts.
The tool uses pdf-lib, which implements this copying entirely in JavaScript and runs at native speed in modern browsers. Because the file never leaves your machine, there is no privacy question about where a contract, medical record or bank statement is being processed, and no retention policy to read. Object streams are enabled on save, which keeps the output compact.
Where merging PDFs is needed
Job applications that must be a single file (CV + cover letter + certificates); scanned receipts combined into one expense claim; contracts assembled from a main body plus signed schedules; visa and immigration submissions that require every supporting document in one PDF; academic theses built from chapter files; monthly statements gathered for an accountant; portfolio pieces stitched together for a client; and print shops that want a single file for a booklet run. Property, legal and HR teams merge hundreds of documents a week.
Merging pairs naturally with the other tools here: convert images to PDF for the photos of your ID, merge them with the form, then split off a copy of just the pages a colleague needs. If a page needs to be sent as a picture — for a chat app or a slide — use PDF to image on the merged file.
Frequently asked questions
Are my PDFs uploaded to a server?
No. Files are read and merged inside your browser with pdf-lib. You can disconnect from the internet after the page loads and it still works.
Is there a limit on file size or number of files?
No fixed limit. Very large batches are constrained only by your device's memory; a few hundred megabytes is fine on a normal laptop.
Can I change the page order?
You can change the order of the files with the ↑ ↓ buttons. To reorder pages inside a file, split it first, then merge the pieces in the new order.
Does merging keep the original quality?
Yes. Pages are copied object by object; nothing is re-rendered or recompressed. Text stays selectable and images keep their resolution.
Why can't I merge a password-protected PDF?
Files that need a password to open are encrypted; unlock them in the app that made them (or with the owner's password) first. Files that only restrict printing or copying merge normally.