PDF Merge
Select up to twenty PDF files and combine their pages into a single download. Pages are copied in file order, preserving their existing page content where the PDF library supports it. Processing occurs locally, with a 50 MB per-file safety limit.
Runs locally — files stay on your deviceHow are merged PDF pages ordered?
Files are processed in selection order, and every file keeps its existing internal page order.
Merging PDF page trees
A PDF document contains page objects and shared resources such as fonts and images. Merging copies pages from source documents into a new document and reconnects the resources those pages need.
How it works
Each selected PDF is loaded with pdf-lib. All page indices are copied into a new PDF in selection order, then the resulting bytes are downloaded.
When to use it
- Combine scanned chapters into one handoff.
- Join an invoice and supporting pages.
- Create one packet from several PDF exports.
When not to use it
- Do not use it to visually flatten annotations or forms.
- Do not expect bookmarks to be rebuilt.
- Do not merge confidential documents on a device you do not trust.
Worked examples
Report packet
- Input
cover.pdf + report.pdf + appendix.pdf- Expected output
merged.pdf
Every page follows the selected file order.
Monthly invoices
- Input
jan.pdf + feb.pdf + mar.pdf- Expected output
One chronological PDF
Source pages remain separate pages.
Scanned sections
- Input
section-a.pdf + section-b.pdf- Expected output
Combined scan
Raster scan quality is not recompressed by intention.
Common mistakes
Selecting files in the wrong order
Merge order follows the browser selection order. Correction: Review filenames and selection order first.
Expecting smaller output
Merging combines resources and is not compression. Correction: Use a dedicated compression workflow if needed.
Assuming interactive forms combine perfectly
Fields with duplicate names or advanced features can conflict. Correction: Test the merged form or flatten a trusted copy first.
Related operations and differences
PDF Split
Split creates a smaller document from selected pages of one source.
Extract PDF Pages
Extraction selects pages from one PDF rather than joining several files.
Limitations and privacy
- Encrypted or damaged PDFs may fail to load.
- Bookmarks, signatures, forms, and uncommon PDF features may not survive as expected.
- Large documents consume browser memory.
Processing uses browser APIs on this device; the entered content is not sent to the Toolbox server.
Frequently asked questions
Does merging upload my PDFs?
No. Selected files are read by browser code and the merged bytes are downloaded locally.
What determines page order?
The selected file order, followed by each file's internal page order.
Will digital signatures remain valid?
Creating a new document can invalidate document-level signatures; verify signed workflows separately.
Does merging compress PDFs?
No. The operation combines pages and resources.
References
- pdf-lib documentation — pdf-lib