Combine multiple PDF files into one document
A PDF is not a single continuous stream and it is a collection of numbered page objects plus metadata (bookmarks, form fields, embedded fonts, images) tied together by a cross-reference table. Merging PDFs is therefore not string concatenation; it is building a new PDF whose page tree references the right subset of objects from each source file, with the cross-reference table rewritten so page numbering stays consistent. A naive concatenation of two PDFs produces a file that either will not open or shows only the first source's pages. This merger handles the object rewriting correctly. Built on pdf-lib, it loads each source file and copies its pages (using copyPages) into one new document in the order you set, then writes a fresh cross-reference table. Upload any number of source files, reorder them by dragging, and export a single output with sequential page numbers. Each page keeps its own embedded resources (fonts, images), so the visible content of every page is preserved exactly. There is also a "Download as ZIP" option that bundles the unmerged source files together instead of combining them.
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A signed contract, an appendix, and a cover letter are three PDFs that must go to the client as one document.
Input
cover.pdf + contract.pdf + appendix.pdf (drag to order)
Output
bundle.pdf, pages in the set order, bookmarks preserved
Pages are concatenated in the order you arrange them while keeping each source’s page size and internal links intact. It runs in the browser, so a confidential contract is never uploaded.
A PDF is not a single continuous stream and it is a collection of numbered page objects plus metadata (bookmarks, form fields, embedded fonts, images) tied together by a cross-reference table. Merging PDFs is therefore not string concatenation; it is building a new PDF whose page tree references the right subset of objects from each source file, with the cross-reference table rewritten so page numbering stays consistent. A naive concatenation of two PDFs produces a file that either will not open or shows only the first source's pages. This merger handles the object rewriting correctly. Built on pdf-lib, it loads each source file and copies its pages (using copyPages) into one new document in the order you set, then writes a fresh cross-reference table. Upload any number of source files, reorder them by dragging, and export a single output with sequential page numbers. Each page keeps its own embedded resources (fonts, images), so the visible content of every page is preserved exactly. There is also a "Download as ZIP" option that bundles the unmerged source files together instead of combining them.
Combine cover page, table of contents, chapters, and appendices from separate files into one polished report.
Merge monthly invoices into a single document for accounting or client records.
Join a resume, cover letter, and reference letters into one PDF for job or grant applications.
Combine exhibits, declarations, and forms into the required filing order.
The merger works on the PDF object model directly using pdf-lib. For each source it calls PDFDocument.load, then copyPages over every page index, and addPage into a single output document, finishing with PDFDocument.save. Because page content streams (the actual drawn marks) are copied as objects rather than re-rendered, output pages are visually identical to source pages, no rasterization, no re-encoding of embedded images, and no quality loss on text or vector graphics.
Page sizes are preserved per page, not normalized. A document merging A4 and US Letter sources will have mixed page sizes in the output, matching each source's original dimensions. This is usually what you want for reports combining documents from different regions.
A few honest limitations follow from how pdf-lib copies pages. Outline bookmarks and document-level form field structures are not specially rebuilt or merged by this tool, so do not rely on a combined table of contents or on form fields from different sources being kept distinct. Encrypted PDFs are a harder case: a password-protected source generally cannot be loaded for copying until it is unlocked first. And because a digital signature covers the entire original document hash, merging a signed PDF into a new document invalidates that cryptographic signature even though the drawn signature mark stays visible on the page. This is a property of the PDF signing standard, not a bug in the merger.
There is no hard limit. Performance depends on your browser and the total file size, but merging dozens of typical documents works smoothly.
Yes. Pages are copied as PDF objects rather than re-rendered, so text stays selectable and vector graphics and images keep their original quality. Note that document-level outline bookmarks are not specially rebuilt when files are combined.
You will generally need to remove the password first, since an encrypted file cannot be loaded for copying until it is unlocked.
PDF parsing and editing happen in your browser. Documents, and everything inside them, are never uploaded or stored remotely.