PDF Merge

Typical reasons to merge PDFs: gluing an invoice and its request form into a single expense attachment, ordering a résumé, certificate scans and portfolio for an application, or assembling chapters written separately into one deliverable. The tool uses pdf-lib to copy every page of each selected file, in list order, into a new PDF. It only concatenates: you cannot pick a subset of pages (use PDF Split for that), and it does not recompress or alter page content.

How to use it

1. Click the dashed box "Click to select multiple PDF files (multi-select allowed)" and pick one or more PDFs. Click again to add more; new files go to the end of the list.
2. Check the "Merge order (top to bottom)" list. Use the ↑ and ↓ buttons on each row to reorder and the trash icon to remove a file.
3. Once there are at least 2 files the button reads "Merge these N files". Click it.
4. When it finishes, the browser downloads the result directly. The filename is always "merged-result.pdf".

Example: ordering three files

Suppose you added cover.pdf (1 page), body.pdf (10 pages) and appendix.pdf (3 pages), numbered 1, 2, 3. If the appendix should come before the body, press ↑ on the appendix row twice and the numbers renumber. The merged PDF has 14 pages, in list order from top to bottom, with each file's own page order intact. Because the output name is fixed, repeated merges will download files with the same name, so rename each one right away.

Supported range and known limitations

• Only files the browser reports as PDF are accepted; anything else is silently ignored when you select it, with no message.
• A password-protected or damaged PDF makes the whole merge fail with "Merge failed. Please make sure all files are valid PDFs, or try a different set of files." It does not skip the bad file and does not say which one it was.
• Only the pages are copied. Document-level structures such as bookmarks or outlines are not carried into the result, and form-field state is not guaranteed to survive.
• The same file can be added more than once and will appear more than once in the output.
• The grip icon on each row is decoration; there is no drag-and-drop, only ↑ and ↓.
• All files are loaded into browser memory, so very large totals are slow and in extreme cases can crash the tab.
• Images are not recompressed, so the result is roughly the combined size of the inputs; run it through PDF Compress afterwards if you need it smaller.

I chose files but the list stays empty.

Either the files were not PDFs (they are filtered out silently), or you picked the exact same file again: the input is not cleared after a selection, so the browser may not fire a change event. Choose a different file or reload the page.

It says the merge failed. What should I check?

Most likely one file is password-protected or corrupted. Test by merging two files at a time to find the culprit, then replace it with an unencrypted copy.

Some pages have different sizes or orientation.

The tool does not rewrite pages, so A4 and landscape or odd-sized pages sit side by side as they are. Normalize the sources before merging if you need uniform pages.

Do my original files change?

No. They are only read; a new file is built in memory and downloaded, leaving the originals untouched.

Privacy and processing

The code contains no upload request. Reading, joining and building the download all happen in your browser with pdf-lib, and nothing is sent to a server. Opening the page loads only the pdf-lib code shipped with the site; no model is downloaded.