PDF Merger

This PDF merger joins several PDF files into one document without uploading anything. You add the files, arrange them in the order you want, and optionally narrow each one to a page range such as 1-3, 5, 8-10 or rotate its pages in ninety degree steps. A thumbnail of the first page and a page count appear beside each file so you can confirm you picked the right document. The merged file is named by you and downloaded straight from the page. It suits anyone assembling a submission from separate parts: scanned receipts into one expense claim, chapters into a single report, certificates into one application pack, or a contract with its signed annexes. Because the work is done by a JavaScript PDF library running in the page, the files stay on your machine throughout and no copy is sent to a server.

When you add a PDF, the page reads it as raw bytes and hands those bytes to pdf-lib, which parses the document structure and reports how many pages it contains. A second library, pdf.js, renders the first page to a small canvas so you get a visual thumbnail. Both run inside the browser tab, so the file itself never leaves your device.

Ordering matters: the merged document follows the order of the list on screen, top to bottom, and you can move entries until it reads correctly. A page range box beside each file accepts single pages and hyphenated spans separated by commas, and the tool validates the range against that file's real page count before it will merge.

On merge, pdf-lib creates an empty document and then copies the selected pages from each source file in turn into that new document. Copying preserves the original page content rather than re-rendering it as an image, so text stays selectable and quality is unchanged. Any rotation you set is applied to the copied pages, and the finished document is serialised back to bytes and offered as a download under the file name you chose.

Say you have three PDFs: a twelve page report, a four page cover letter and a twenty page appendix.

You want the cover letter first, so you move it to the top of the list and leave its range empty, which means all four pages are used. Next comes the report, but only its summary and one chart: you type 1-3, 7 in its range box. That is pages 1, 2, 3 and 7, which is four pages. Last comes the appendix, narrowed to 5-8, another four pages.

The merged document therefore contains 4 plus 4 plus 4, which is twelve pages. They appear in exactly that order: cover letter pages 1 to 4 become pages 1 to 4 of the output, the report's pages 1, 2, 3 and 7 become pages 5 to 8, and the appendix's pages 5 to 8 become pages 9 to 12.

If the appendix had been scanned sideways, clicking its rotate control twice would apply 180 degrees to those four pages only, leaving the other two files untouched. Name the output submission and it downloads as submission.pdf.

Open the merged file and check three things: the page count matches what you expected, the order reads correctly, and any rotated pages are the right way up. The page count is the quickest check, because a range typed as 1-3,5 gives four pages while 1-5 gives five, and an off-by-one here is the most common mistake.

A range referring to pages that do not exist is rejected rather than silently ignored, so a warning next to a file usually means you typed a number larger than that document's page count. Remember that ranges are per file and always count from that file's own page 1, not from the position of the file in the merged output.

Merging copies pages; it does not repair them. A scanned page with no text layer stays unsearchable, and a page that was blurry stays blurry. Form fields, bookmarks and internal links may not survive the copy, so treat interactive PDFs with care and check them afterwards. Encrypted or password protected files cannot be read at all and must be unlocked before they can be added.