PDF Merger – Merge PDF Files Online Free
PDF Merger is a free online tool that combines multiple PDF files into a single document using the pdf-lib library — entirely in your browser. Upload up to 5 PDFs, drag to reorder them, then click Merge. The merged file is assembled in memory and downloaded directly — nothing is sent to a server.
Your files never leave your device. All merging is done locally using pdf-lib + WebAssembly. No upload, no server, no storage.
How to Merge PDF Files Online Free
- 01
Upload your PDFs
Drag and drop or click to select up to 5 PDF files. The page count for each file is shown automatically.
- 02
Reorder if needed
Drag the grip handle to reorder files. The merged document will follow the order shown in the list.
- 03
Merge and download
Click "Merge PDFs". pdf-lib processes everything in your browser, then offers the merged file for download.
Features
- ✓Merge up to 5 PDFs in one session
- ✓Drag-and-drop reordering before merge
- ✓Page count shown per file
- ✓Progress bar during merge
- ✓Max 10 MB per file
- ✓100% client-side — pdf-lib + WebAssembly
- ✓No login, no file upload to server
- ✓Upgrade prompt for 6+ files
Frequently Asked Questions
How does browser-based PDF merging work?
The tool uses the pdf-lib library compiled to WebAssembly to read each PDF, copy all its pages into a new document, and export the result as a Blob. The merged file is then made available for download via a local object URL. No file is ever sent to a server.
Can I reorder PDFs before merging?
Yes. Drag the grip handle on the left of each file row to reorder them before clicking Merge. The merged PDF will contain pages in the order shown in the list.
What is the file size limit per PDF?
The free plan supports files up to 10 MB each and up to 5 files per session. These limits exist because processing happens in browser memory. Very large PDFs (over 10 MB) would risk running out of available memory.
Will encrypted or password-protected PDFs work?
Encrypted PDFs may fail to load. The tool attempts to read them with ignoreEncryption mode, but if the file requires a password, merging will fail and an error will be shown. Remove encryption from the PDF first using your PDF reader.
Does merging change the content or quality of the PDF?
No. pdf-lib copies pages from the source documents at the byte level — text, images, fonts, and formatting are preserved exactly. The merged PDF is structurally identical to having all pages in one document, with no re-rendering or quality loss.