Organize
Merge PDF files
Combine two or more PDFs into one document. Upload your files, drag to set the order you want, and click Merge. The output is a single PDF containing every page from every file in the order you arranged them. All processing runs in your browser; no files are sent to a server.
Drop PDF files here
or click to browse · PDF only · multiple files allowed
How this tool handles files
- Processing
- In your browser, on-device
- Storage
- Nothing stored
- Output
- A file you download
- Your responsibility
- Review before official use
- Runs in your browser. Your file is processed on your own device and, on this site, is not uploaded to our servers.
- Nothing is stored. Your file and its output are gone the moment you close or reload the page.
- Review sensitive files (bank, ID, medical) and check the output before sharing it.
Every tool on FormatOS runs in your browser. Read our Privacy Policy and File Handling Policy.
How it works
- 1
Upload your PDFs
Drop two or more PDF files onto the upload area, or click to browse. Files are read immediately in your browser — nothing is sent to a server.
- 2
Arrange the order
Drag file rows up and down to set the page order. The number badge next to each row shows its position. Pages appear in file order within each file.
- 3
Merge
Click Merge. pdf-lib reads each file, copies pages in the order you set, and builds a new PDF in your browser memory.
- 4
Download
When the merge is complete, click Download PDF. The file is saved directly to your device. It is not uploaded or stored anywhere.
Common uses
- Combine a cover letter and CV into one PDF
- Bundle multiple invoices into a single file for an accountant
- Assemble a multi-chapter document from separate exports
- Package supporting documents into one attachment
Limitations
- Encrypted or password-protected PDFs cannot be merged.
- Very large files may hit browser memory limits.
- Merge preserves page content but may not preserve embedded scripts or interactive form fields from all sources.
Input
PDF files only. Each file must be a valid, unencrypted PDF.
Output
A single merged PDF file ready to download.
When merging is the right move
Merging shines when several PDFs really belong together as one file: a cover letter and a CV for a job application, a stack of invoices for an accountant, signed contract pages returned separately, or a set of chapter exports that should read as a single book. Combining them first means the reader scrolls one document instead of juggling attachments, and page references stay meaningful end to end.
A common, reliable pattern is to merge last. Get each source PDF the way you want it — rotate a sideways scan, drop a blank page, extract just the pages you need — and only then combine them. If you also want continuous numbering across the whole bundle, merge first and add page numbers as the final step so the count never resets between sections.
Order is set by you, not guessed. Drag the file rows up and down before you click Merge; within each file, pages keep their original sequence. If two files share a name, the tool keeps both rather than silently dropping one, so nothing goes missing from your final document.
What survives the merge — and what may not
Page content is copied faithfully: text, vector graphics, and embedded images come across exactly as they appear in each source file. For the vast majority of everyday documents — reports, scans, statements, slide exports — the merged PDF looks identical to the originals stacked back to back.
Interactive and structural extras are where PDFs differ. Form fields, bookmarks (the outline tree), internal hyperlinks, and embedded JavaScript may not carry through depending on how each source was produced, because those layers are stored differently across PDF generators. If a document relies on a fillable form or a clickable table of contents, check the merged result before you send it.
Encrypted or password-protected PDFs can't be merged — they're rejected with a clear message rather than producing a broken file. Remove the protection from a document you own first, then merge. Very large files can also hit browser memory limits; if that happens, merge in smaller batches and then combine the results.
Files stay on your device
Merging runs entirely in your browser using the pdf-lib engine. Each file is read, its pages are copied into a new document in the order you set, and the finished PDF is handed back to you as a download. Nothing is uploaded to a server, which matters for contracts, financial records, and anything else you'd rather not transmit — a good fit for sensitive paperwork.
Because the work happens in memory, closing or reloading the tab clears everything. Keep your original files until you've confirmed the merged PDF is correct; there's no server-side copy to fall back on, and that's by design.
Frequently asked questions
There is no hard limit on the number of files. In practice, browser memory limits the total uncompressed page data. If you hit memory errors, merge in smaller batches and then re-merge the results.
Page content and embedded images are preserved. Interactive elements such as form fields, bookmarks, and JavaScript actions may not survive the merge depending on how the source PDFs were produced.
No. The merge runs entirely in your browser using pdf-lib. Your files stay on your device.
No. Encrypted or password-protected PDFs are rejected with an error message. Remove the password first using a trusted tool, then merge.
Pages appear in the order of the files in your list. Drag file rows to reorder them before merging. Within each file, pages appear in their original order.