How the PDF Merger Works
DocDox PDF Merger combines multiple PDF files into a single unified document entirely within your web browser. Unlike cloud-based services that require uploading files to a remote server, this tool uses pdf-lib — a powerful open-source JavaScript library — to merge your PDFs locally. Your files never travel across the internet and are never stored anywhere.
Select two or more PDF files using the upload area or by dragging them directly into the tool. Rearrange their order before merging, then click "Merge PDFs." The process takes seconds even for large documents, because it runs directly on your device CPU without any server round-trips.
The output PDF preserves all original formatting, embedded fonts, images, and metadata from each source file. Pages are appended in sequence with no re-rendering or quality loss.
Do my PDFs get uploaded to a server?
No. All merging happens in your browser using JavaScript. Your files never leave your device.
Is there a limit to how many PDFs I can merge?
There is no server-imposed limit. Performance depends on your device — most modern computers handle dozens of PDFs without issue.
Will the merged PDF be compressed or reduced in quality?
No. Pages are combined exactly as they appear in the source files with no recompression or quality change.