Local PDF Merge Tool
A free, browser-based file tool. Runs entirely in your browser — no sign up, nothing stored.
Drag & drop PDFs here, or
Your files are merged on your device and never uploaded.
How to use this calculator
- Drag your PDFs onto the box, or press “Choose PDF files”.
- Drag-reorder isn't needed — use the ↑ ↓ arrows to set the order they'll join.
- Press “Merge PDFs”, then download the combined file.
How it works
The tool reads each PDF in your browser, copies every page in the order you set, and writes them into a single new PDF — all on your device using the pdf-lib library.
Nothing is uploaded. Your files never leave your computer, which is why it works offline once the page has loaded.
Tips
- Use the arrows to get the page order right before merging.
- The result downloads as “merged.pdf”.
Frequently asked questions
Are my files uploaded anywhere?
No. The merge happens entirely in your browser — your PDFs are never sent to Zerdly or any server.
Why won't one of my PDFs merge?
Password-protected or corrupted PDFs can't be read. Remove the password first, then try again.
Is there a file size limit?
Only your device's memory — very large files use more RAM since everything runs locally.
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.