Merge PDF Files
Combine multiple PDF files into one document online, free. Drag to reorder pages and see page counts before merging, private, no uploads, no limits.
About This Tool
Combine multiple PDF files into a single document in seconds. Simply upload your PDFs, drag them into the order you want, and merge. The page count for each file is shown so you know exactly what you're combining. No page limits, no watermarks, no account required. The merge happens entirely in your browser using the pdf-lib library, your documents never leave your device.
How To Use
- Upload two or more PDF files by dragging them into the drop zone.
- Drag files up and down to arrange them in your preferred order.
- Review the page count shown for each file to confirm your selection.
- Click "Merge" to combine and download the single merged PDF.
How It Works
PDF merging works by creating a new empty PDF document and then copying pages from each source file into it, one after another, using the pdf-lib library. This is a genuine page-level copy operation, all text, images, fonts, annotations, and formatting from each source PDF are preserved exactly as they were in the original files.
The order of pages in the merged PDF matches the order you arrange the files in the list. If File A has 5 pages and File B has 3 pages, the merged PDF will have 8 pages: A1-A5 followed by B1-B3. Each source PDF is loaded independently, so different page sizes, orientations, and formatting are all handled correctly.
The processing happens in a Web Worker to keep your browser responsive. For very large PDFs (50+ MB), the operation may take a few seconds as each page must be parsed and copied. Memory is managed carefully by processing files sequentially rather than loading all source PDFs into memory simultaneously.
Frequently Asked Questions
Is there a limit on the number of files?
You can merge up to 50 PDF files at once. Each file can be up to 100MB. There is no limit on the total number of pages in the merged output, merge documents with hundreds of pages without issue.
Will the formatting be preserved?
Yes. Merging copies pages at the PDF level, preserving all text, images, fonts, links, and formatting exactly as they appear in the original files. No content is re-rendered or modified.
Can I merge password-protected PDFs?
Not directly. You'll need to remove the password first using our Remove PDF Password tool, then merge the unprotected files. We'll show a helpful link if you upload a protected file.
Can I reorder the files?
Yes. After uploading, drag and drop files in the list to arrange them in any order. The merged PDF will follow the exact order shown. Each file's page count is displayed for easy reference.
Does merging increase the file size?
The merged file size is approximately equal to the sum of the input file sizes, sometimes slightly less due to deduplication of shared fonts and resources. No additional compression is applied.
Are my PDFs uploaded to a server?
No. All merging happens locally in your browser using the pdf-lib JavaScript library. Your documents never leave your device and are never transmitted over the internet.