🧷 Merge PDF
Upload two or more PDFs and merge them into a single file — entirely in your browser.
About Merge PDF
Merging combines two or more PDF files into a single document, page for page, in the order you add them. It's the tool for pulling together a multi-part report, stitching scanned pages from separate sessions into one file, or combining several invoices, contracts, or chapters before sending one document instead of a handful of attachments. There's no separate reordering step — files merge in the sequence you add them, so remove and re-add a file to move its position.
The merge runs entirely through pdf-lib.js, a JavaScript library that reads and writes the raw structure of a PDF. Each source file is loaded into a PDFDocument object, and its pages are copied — content streams, fonts, and images included — into a new document with copyPages(), which is then serialized into the file you download. Because pages are copied as structural objects rather than re-rendered, there's no quality loss: vector text stays vector, and embedded fonts and images stay exactly as they were.
Two things worth knowing: pdf-lib doesn't carry over bookmarks or outline navigation from the source files, so a merged PDF loses any table-of-contents-style navigation the originals had. And if more than one of the files you're merging already contains a fillable form, overlapping field names can cause values to become linked or overwritten in the merged form, since PDF viewers treat identically named fields as one field across the whole document.
Frequently asked questions
Is there a limit to how many PDFs I can merge?
No hard limit — it depends on your device's memory since everything happens in your browser. A handful of typical documents merges instantly.
Can I reorder the files before merging?
Files merge in the order you add them. Remove and re-add a file to move it, or add files one at a time in your preferred order.
Will this work with password-protected PDFs?
Encrypted PDFs generally can't be merged until the password is removed first.
Do bookmarks or a table of contents carry over when merging?
No — pdf-lib copies page content but not the document outline, so any bookmarks or navigation links from the original files won't appear in the merged PDF.
What happens if two merged PDFs have forms with the same field names?
Because PDF viewers treat identically named form fields as one field across a document, merging two forms that share field names can cause their values to become linked or overwritten. Rename fields first if you need them to stay independent.
Does the merged file keep each PDF's original page size?
Yes — pages are copied exactly as-is, so combining a letter-size page with an A4 page keeps each page at its own original dimensions rather than resizing everything to match.