Merge PDF
Drop any number of PDF files, drag them into the order you want and download a single merged PDF. Everything runs in your browser with pdf-lib — files never leave your device.
Merging happens entirely in your browser. Your PDFs never leave your device.
How to use this merge pdf
- Drop or pick one or more PDF files.
- Drag the file list to set the order — page 1 of the first file goes first.
- Drop additional PDFs anytime to append them.
- Click Merge & download to save a single combined PDF.
Frequently asked questions
Why do form fields stop working when I merge two fillable PDFs?
Both source PDFs likely use the same internal field names (Name, Date, Signature). When merged they collapse into one field — typing in 'Name' on page 1 changes 'Name' on page 5. Flatten the form fields in each source PDF first (turn them into permanent text), then merge.
How large a merge can my browser handle?
Up to several hundred MB on desktop with 16 GB RAM; on mobile and older laptops you'll hit memory limits around 100-150 MB total. The whole job runs in-memory because there's no server doing the lifting.
Are bookmarks and form fields kept?
Pages and their content are copied. Bookmarks, form fields and most annotations are preserved by pdf-lib but some advanced PDF features may be flattened.
Can I reorder files after adding them?
Yes. Drag any file in the list, or use the up/down arrows. You can also remove individual files before merging.