Why Merge PDFs Locally?
Merging PDFs is one of the most common document tasks in any office. You might need to combine a cover letter with a resume, assemble a report from multiple chapters, or package invoices for accounting. The typical workflow involves uploading all your files to a cloud service — which means your documents are sitting on someone else's server.
With HarborConvert, the merge happens entirely inside your browser. No upload. No wait. No data leaving your device.
How It Works
HarborConvert uses pdf-lib, a pure JavaScript PDF library, to handle the merge. When you drag in multiple files:
- Each PDF is read into your browser's memory
- pdf-lib extracts all pages from each document
- The pages are assembled into a single new PDF in memory
- The result is offered as a download — it never touches our servers
Step-by-Step
- Open the PDF Merge tool
- Drag all the PDFs you want to combine onto the drop zone
- Drag the file thumbnails to reorder them if needed
- Click Merge PDFs
- Download the combined file
Free accounts support up to 1 file at a time (so merging requires a Pro account). Pro accounts can merge up to 10 files in one batch; Business accounts up to 100.
Tips for Better Results
Consistent page sizes: If you're merging documents with different page sizes (A4 with Letter, for example), the output will contain mixed sizes. Most PDF viewers handle this fine, but some printers may have trouble. Use a PDF editor to normalize page sizes if needed.
Page order matters: Take a moment to arrange files in the correct order before merging. Reordering pages in the output is harder than getting the input order right.
Large files: If you're merging large PDFs and the browser tab slows down, it's working — complex PDFs with many embedded images require significant memory. Close other tabs to free up RAM.
What About Password-Protected PDFs?
Password-protected PDFs cannot be merged until they are unlocked. You'll need to enter the password to open the file before it can be processed. If you don't have the password, the file cannot be included in the merge.
Alternatives
If you need to merge more than 100 files, or if your files exceed 200 MB each, you may need a desktop tool like LibreOffice Draw or Adobe Acrobat. For most everyday merging tasks, the browser-based approach is faster and more private.