Merge PDF Files Locally
Combine multiple PDFs into one document in your browser, then optionally compress the merged file for easier sharing. No uploads, no accounts, no waiting on a server.
Drop files here or browse
Supports PDF - up to 20 files, 50 MB each
Why use the PDF merger?
Merge in your browser
Your files stay on your device from upload through final download.
Choose the order
Move files up or down before merging so the final document is arranged exactly how you need it.
Compress after merging
Once the combined PDF is ready, you can run the same local PDF compression flow without re-uploading.
How local PDF merging works
Add at least two PDF files, arrange them in the order you want, and start the merge. pdf-lib loads each source file, walks its page tree, and copies each page object — fonts, images, and vector content included — into a freshly created destination PDF document, in the exact order your file list is arranged in. Nothing is rasterized or re-encoded during a merge; a page copied this way is byte-for-byte the same content as the original, just relocated into a new container document. That's why merging never introduces the kind of quality loss that compression does — it's structural surgery on the PDF's object graph, not a re-render.
After the merged document is ready, you can download it immediately or run local PDF compression to reduce file size. That is useful when the combined document becomes too large for email attachments, forms, or messaging apps — five originally-reasonable PDFs can easily add up to something over a typical 10-25MB attachment cap once combined.
If one of your files is invalid or password-protected, the tool will stop and let you know which file could not be opened, rather than silently producing a merged document that's missing pages.
- 1Add PDF files. Click to select or drag in two or more PDF files. Arrange them in your preferred order.
- 2Reorder files. Drag files up or down in the list to set the final page order before merging.
- 3Merge and download. Start the merge. Your browser combines all pages into a single PDF locally. Download the result directly. No server upload needed.
Merge order and follow-up, by situation
| Situation | What to do | Why |
|---|---|---|
| Combining a cover letter, resume, and portfolio into one PDF | Order them cover letter → resume → portfolio before merging | The merge preserves whatever order the file list shows — there is no automatic reordering by filename or date, so arrange it exactly as the reader should see it. |
| The combined file needs to clear a 5MB or 10MB upload cap | Merge first, then compress the merged result — not each file individually | Compressing each source file first wastes quality budget on pages that end up as a small fraction of the final document; compressing once, after merging, lets the algorithm allocate quality across the whole combined page count. |
| One of the source files is password-protected | Unlock it first (you'll be prompted), then merge | The merge tool needs to read the actual page content to copy it into the new document, so an unreadable encrypted file has to be opened before its pages can be included. |
| Merging many short PDFs (10+) into one long document | Double-check the order in the list before merging — reordering after the fact means re-merging | There's no in-place page reordering once the merge is done; the merge produces a flat new PDF, so getting the file order right up front saves a redo. |
Known limits
Merging doesn't shrink anything — the combined file's size is close to the sum of its parts, since pages are copied, not recompressed. If the result needs to fit a size limit, treat merging and compressing as two separate steps in that order.
Merging a very large number of files, or files with many embedded high-resolution images, uses memory proportional to the combined document size, since the whole merge happens in your browser tab's memory rather than streaming to disk the way a desktop tool might.
Need the merged PDF under 1MB?
Download your combined file, then open the free Compress PDF tool and set a 1MB target. It shrinks the merged document to fit email or upload limits, still entirely in your browser.
Frequently asked questions
How many PDF files can I merge at once?
You can merge as many PDFs as you need. There is no hard limit on the number of files. However, very large batches may take longer to process depending on your device.
Will the merged PDF keep the original page order?
Yes. Pages are added to the merged document in the order your files are arranged in the list. You can drag files to reorder them before merging.
Can I merge password-protected PDFs?
Yes. If you upload a password-protected PDF, you will be prompted to enter the password. After unlocking, the file can be merged normally.
Does the merge tool need to send my files anywhere to combine them?
No — combining PDFs doesn't require a server at all, which is easy to lose sight of since most online mergers use one anyway. pdf-lib loads each file's byte stream, copies its page objects into a new PDF document object, and serializes that back to bytes — all standard JavaScript operating on data already in your browser's memory. There's no step in that process where a network request would even help.
How do I merge PDFs and get the result under 1MB?
Merge your files here and download the combined PDF, then open Compress PDF and set a 1MB target. Merging keeps full quality, and the compressor shrinks the result to fit email or upload limits. Both tools run locally in your browser.
Learn more
From the blog
How to compress PDF for email
Merged PDFs often end up oversized — here is how to bring the result back down.