Combine multiple PDF documents into a single file. Selected file contents are processed locally in your browser.
Local-first PDF merging
Drag in your PDF files, reorder them as needed, and merge them into one. Everything happens in your browser memory.
PDFs are processed in your browser. File contents are not intentionally uploaded by this tool.
ConvertUnlimited uses pdf-lib, a modern browser-side library for PDF manipulation. When you add files, they are decoded locally in your browser. Our tool then iterates through the pages of each document and copies them into a single, fresh PDF archive based on your preferred order.
Since the merging happens entirely on your own machine, your document contents are processed locally in your browser. This reduces server-side exposure for sensitive contracts, legal documents, and personal records.
Unlike cloud-based "Join PDF" services that keep copies of uploaded data on a server, ConvertUnlimited provides the merge logic as a static script that runs in this tab. Selected file contents are processed locally in your browser for this workflow, and ConvertUnlimited does not provide a server-side upload endpoint for it.
This tool uses pdf-lib (version 1.17.1). When a file is added, pdf-lib parses its cross-reference table and object graph, then copyPages() copies the selected page objects — along with the fonts, embedded images, and other resources those pages reference — into a new PDFDocument; a final save() call serializes that document into PDF bytes. Because pages are copied as objects rather than rendered and redrawn, merging does not rasterize or re-compress embedded images and does not reduce text sharpness. The output is a structural recombination of the inputs, not a re-encode.
This also explains why encrypted PDFs fail immediately: the tool calls PDFDocument.load() without an ignoreEncryption option, so a password-protected file throws an error before any pages can be read. There is no in-browser password prompt for this tool; a source PDF must already be decrypted before it is added.
pdf-lib keeps each copied page's own page-size box, so combining documents of different sizes does not normalize or stretch them to match:
| Page size | Millimeters | Points (1/72 in) |
|---|---|---|
| A5 | 148 × 210 mm | 420 × 595 pt |
| A4 | 210 × 297 mm | 595 × 842 pt |
| A3 | 297 × 420 mm | 842 × 1191 pt |
| US Letter | 216 × 279 mm | 612 × 792 pt |
| US Legal | 216 × 356 mm | 612 × 1008 pt |
A merged file combining an A4 report with a US Letter invoice, for example, keeps each page at its original size when opened; ConvertUnlimited does not resize pages to make the document uniform.
A merged PDF lands close to the sum of its inputs' page content, plus a small amount of overhead from the new cross-reference table that save() writes. For example, combining five roughly 2 MB single-topic PDFs typically produces a file close to 10 MB — merging itself does not compress. pdf-lib also does not deduplicate identical resources across separate source files: if two input PDFs happen to embed the exact same logo image, each copy is carried over as its own object rather than merged into one shared resource, since the library has no practical way to detect that two byte streams from different files are identical without decoding and hashing them. Use Compress PDF afterward if the combined file needs to be smaller.
We don't impose a limit on the number of files, but very large multi-hundred-page documents may exceed your browser's RAM capacity. If the tool crashes, try merging fewer documents at once.
Yes. The tool preserves the original page order within each document and follows the sequence you set in our file list workbench.
Password-protected files cannot be merged for security reasons unless they are decrypted first. Please use a tool to remove the password before merging.
No. pdf-lib copies existing page objects, including embedded images and fonts, rather than rasterizing pages and redrawing them, so merging by itself introduces no generation loss. If you need a smaller file afterward, run the result through Compress PDF.
Yes. pdf-lib preserves each page's own dimensions, so a merged file can mix A4, US Letter, and other page sizes; each page keeps its original size when opened.
Each source file's form fields are copied along with its pages. If two source PDFs use the same field name, most viewers keep them as separate, unlinked fields, though behavior can vary by PDF viewer.
No. The output PDF contains only the copied pages in the order set in the file list workbench; ConvertUnlimited does not insert a cover page or watermark.
This tool works in all modern browsers supporting the File API and WebAssembly, including Chrome, Firefox, Safari, and Edge.
Merge multiple PDF files into one for free in your browser. Reorder pages and join PDF documents. No signup or watermark. File contents are processed locally in your browser for supported workflows.
Use the controls on this page, review the output in your browser, then download the result from this tab.
Files are processed locally where supported. Review the Trust Center for the processing model and the Privacy Policy for public-site privacy boundaries.