Merge PDF

Merge PDF files into one tidy document. Add your PDFs, drag to reorder, then download — all in your browser, nothing uploaded.

How to use Merge PDF

  1. Add the PDF files you want to combine (drag & drop or browse).
  2. Drag the files into the order you want them to appear.
  3. Click “Merge PDF” to build the combined document.
  4. Download your merged PDF.

About Merge PDF

Merging is a structural operation, not a re-rendering one. A PDF is a graph of numbered objects — page dictionaries, embedded font programmes, image XObjects, content streams — and pdf-lib walks that graph for every file you add, copies the objects each page depends on into a new document, and renumbers the references so nothing collides. No page is ever decoded to pixels and encoded again on the way through. That is why the combined file is visually identical to its sources rather than a generation-loss copy of them, and why forty megabytes of scans come out at roughly forty megabytes.

The reason that mechanism is worth explaining is that the documents people combine are rarely trivial. Signed contracts, mortgage paperwork, discharge summaries, three months of statements for a visa application — these are exactly the files that end up queued on an unknown server when you use a typical online merger. Here they are read straight from disk by the browser, assembled in this tab’s memory, and handed back as a download. There is no transfer to trust, no temporary copy on somebody else’s hardware, and no retention policy to take on faith.

A few document types behave differently, and it is better to know before you start. Encrypted files are refused outright: while a PDF is locked its page objects cannot be parsed, so the tool stops with a plain message instead of writing a corrupt output that looks fine until somebody opens it. Take the password off in a reader first. Interactive form fields survive the copy, but two forms using the same internal field names will share their values afterwards, which is worth checking on anything you still intend to fill in.

There is no file-count ceiling and no size cap, because there is no server whose bandwidth bill would justify one. The genuine constraint is memory: every source stays resident while the combined document is built, so twenty five-megabyte files are comfortable on any laptop while a single half-gigabyte scan can exhaust a budget phone and reload the tab. On mobile with very large inputs, work in two or three passes. Sequence comes from the order of the cards on screen, so arrange them before pressing the button — what you see is what gets written.

Frequently asked questions

Is it safe to merge confidential PDFs online?

Safer than the usual alternative, because nothing is transmitted. The whole operation runs inside this tab, so your document never reaches a server, never joins a processing queue and is not subject to anyone else’s deletion schedule. You can check it for yourself: open your browser’s network panel, run a merge, and watch that no request carries the file.

Will merging reduce quality or make the file blurry?

No. Pages are copied as objects rather than re-rendered, so photographs keep their original compression, text remains vector text, and embedded fonts travel with the pages that use them. Printed, or zoomed to 400%, the result is indistinguishable from the originals.

Can I merge password-protected PDFs?

Not while the protection is in place. An encrypted document hides its page structure from the parser, so you get an explicit error rather than a silently broken download. Open the file in a reader that accepts the password, save an unprotected copy, and combine that instead.

Is there a limit on file size or how many PDFs I can add?

Neither is capped by the tool. Your device’s available memory is the real boundary, since each input is held open until the output has been written. Desktop browsers routinely cope with several hundred megabytes in total; an older phone gives up a good deal sooner.

Does this work on an iPhone or Android phone?

Yes. Pick files through the Files app or the share sheet, drag the cards to set the order, and the finished document saves to your usual downloads location. Mobile Safari reclaims background tabs aggressively, so keep the page in front while a long job runs.

What happens to form fields, links and bookmarks?

Form fields and link annotations attached to a page are carried across with it. Document-level bookmarks are not, because the outline tree belongs to the original file rather than to any individual page — rebuilding it needs a full editor afterwards.

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