PDF Merger

• Fully client-side. PDFs are read with the File API, parsed and combined with pdf-lib, and re-serialised entirely inside your browser. No content is transmitted to any server.
• No tracking. The tool does not record which files you upload or how you order them. There is no analytics on file content.
• No automatic saving. Files are held in memory only. Reloading the page clears everything.
• Encrypted PDFs are not supported. If a file requires a password, remove the password first and save an unprotected copy.
• Page content is preserved. Merging copies the original pages without re-encoding, so text stays selectable and images retain their quality. Interactive form fields and bookmarks may not carry over from every source.
• Memory limits. Total size is bounded by your browser's available memory. Files up to about 100 MB in total work well. Larger jobs may be sluggish.

A practical guide to merging PDFs

PDF is the standard format for sharing documents that need to look the same everywhere. Its strength is that it captures layout, fonts and images exactly, which makes it ideal for contracts, invoices, reports, scans and forms. That same rigidity is why combining several PDFs into one is such a common task: you might need to attach a signed page to a report, join a series of invoices into a single statement, or assemble a submission from multiple scanned chapters.

Why a browser-based merger

There are two common ways to merge PDFs. Desktop software is powerful but heavy, and it often requires installing an application. Online services are convenient but typically upload your files to a remote server, which is a problem for anything confidential. A browser-based merger that runs entirely on the client gives you the convenience of a website with the privacy of a desktop application. Modern browsers expose all the necessary APIs, and JavaScript libraries like pdf-lib can read and write PDFs without sending a byte anywhere.

What merging actually does

Technically, merging PDFs means copying pages from one or more source documents into a new document in a specific order. Each source PDF has its own internal structure — fonts, images and other resources that are shared across its pages. A good merger copies those resources along with the pages, so no quality is lost. A poor merger re-renders each page as an image, which produces a much larger file and removes all text selectability. The tool on this page uses pdf-lib's page-copying API, which preserves the original content streams.

When order matters

The order of the files in the list becomes the order of the pages in the merged PDF. This matters more than it first appears: a signed contract needs the signature page at the end, not the beginning; a report needs its cover first; a series of invoices should follow chronological order. The drag-and-drop interface here lets you rearrange freely, and the up and down arrows on each card give you a keyboard-accessible alternative. Sorting by filename is a fast way to align with alphabetical order when the files are already named in sequence.

Common pitfalls

• Password-protected files. Encrypted PDFs must be unlocked before merging. Save an unprotected copy first.
• Different page sizes. A PDF can contain pages of any size, and the merged output will simply carry those sizes through. If you want a uniform page size, resize the source pages before merging.
• Very large files. Merging runs in memory, so the total size of the sources is bounded by your browser's available RAM. For extremely large jobs, splitting the work into smaller batches can be more reliable.
• Interactive forms. If the sources contain fillable forms, the merged file may not preserve them as editable fields. Flatten the forms first if the recipient only needs to read them.

About this tool

This PDF merger is part of the TempScript free online tools collection. It runs entirely in your browser, requires no account, and never sends your files anywhere. If you work with documents regularly, you may also find our PDF page organizer and image compressor useful.