Drop your PDFs here
or click to browse — select multiple files at once
PDF files only · Processed entirely in your browser
How it works
- 1
Add your PDFs
Drop multiple PDF files onto the tool at once, or click to browse and select them from your device.
- 2
Arrange the order
Use the up and down arrows to set exactly the order you want the pages to appear in the final document.
- 3
Merge and download
Click Merge PDFs and download your single merged PDF file instantly — no waiting, no email.
Why use this PDF merger?
100% private
Your PDFs never leave your device. Everything is processed locally using pdf-lib — no server upload, ever.
Instant, no sign-up
No account or email required. Add files, merge, and download — done in under a minute.
Custom page order
Reorder your PDFs before merging so pages appear exactly where you want them.
Unlimited files
Merge as many PDFs as you need in a single pass — no per-file or per-page limits.
No quality loss
Pages are copied directly without re-encoding, so the merged PDF is identical in quality to the originals.
One-click download
The merged PDF is ready to download immediately — no email, no link expiry.
When would you merge PDFs?
PDFs accumulate quickly — invoices, contracts, reports, scans. Here are the most common reasons to merge them into one file.
Consolidate a multi-part contract
Agreements often arrive as separate cover pages, terms, schedules, and exhibits. Merge them into a single PDF before signing so the document is complete and self-contained.
Bundle invoices for accounting
Instead of sending a dozen individual invoices to your accountant or attaching them one by one to an email, merge them into a single monthly or quarterly PDF.
Assemble a job application
Recruiters prefer a single attachment. Merge your CV, cover letter, portfolio pages, and references into one clean PDF before applying.
Compile a report from multiple sources
Research reports often pull from multiple documents — executive summary, data appendix, charts. Merge them in the right order for a polished, unified deliverable.
Prepare a print-ready booklet
Print services typically accept a single PDF. Merge all sections of a brochure, manual, or booklet into one file before sending to print.
Archive scanned documents
Scanners often produce one PDF per page. Merge multi-page scans into a single, organised document for tidy long-term storage.
How PDF merging works under the hood
No servers, no uploads — here is exactly what happens when you merge PDFs in your browser.
- 01
Files are read locally
When you add PDFs to the tool, your browser reads each file directly from disk using the File API. At no point is any data transmitted over the network — the bytes never leave your device.
- 02
pdf-lib loads each document
The open-source pdf-lib library parses each PDF in JavaScript, understanding its internal page tree, fonts, images, and content streams. No server-side rendering or processing is involved.
- 03
Pages are copied into a new document
A brand-new empty PDF is created. For each source file, pdf-lib copies every page — including all embedded fonts, images, and vector graphics — directly into the new document without re-encoding anything.
- 04
The merged PDF is serialised
Once all pages have been copied in your chosen order, pdf-lib serialises the new document into raw PDF bytes entirely in memory. This step is fast even for large multi-file merges.
- 05
The result is downloaded
The merged PDF bytes are wrapped in a Blob and a temporary object URL is created in the browser. Clicking "Download merged PDF" triggers a standard file-save dialogue — no server roundtrip required.
What to know about the merged PDF
Merging PDFs is straightforward, but a few details are worth understanding before you share or archive the result.
Page content is preserved exactly
Text, images, vector graphics, fonts, and layout are all copied faithfully from the source files. The merged PDF will look identical to the originals — there is no re-rendering or quality degradation.
Bookmarks and outlines are not carried over
If your source PDFs contain a table of contents or bookmarks (named destinations), these are not transferred to the merged file. If you need bookmarks, add them manually using a PDF editor after merging.
Form fields may behave unexpectedly
PDFs with interactive form fields can sometimes conflict when merged if multiple source files contain fields with the same internal name. For best results, flatten interactive forms before merging.
Mixed page sizes are supported
You can merge PDFs with different page sizes — A4, Letter, landscape, portrait — without any issue. Each page retains its own dimensions in the merged file.
Encrypted PDFs must be unlocked first
Password-protected PDFs cannot be merged. Open the protected file in your PDF viewer, remove the password, save a new copy, and then add it to the merge tool.
File size is roughly additive
The merged PDF will be approximately the sum of the source file sizes. If you need a smaller output, use a PDF compressor on the merged file afterwards.
Best practices before you merge
A little preparation before merging will save you time and produce a cleaner final document.
- 01
Review page order carefully
The merged PDF will follow the file order you set in the tool, and each file's internal page order is preserved. Check that the last page of each source document flows naturally into the first page of the next before clicking Merge.
- 02
Remove blank or duplicate pages first
Scanners often produce blank pages between documents, and some PDFs include duplicate cover pages. Use the split or extract tool to remove unwanted pages from individual files before merging them together.
- 03
Standardise page sizes if needed
If the merged PDF will be printed or presented, having consistent page sizes looks more professional. Consider converting source files to a uniform format (e.g. all A4) in a PDF editor before merging.
- 04
Check the file size after merging
Very large merged PDFs can be slow to open and difficult to email. If the result exceeds the size you need, run it through a PDF compression tool to reduce it without visible quality loss.