About Merge PDF
Merging combines the pages of several PDF files into one document, in the order you arrange them. This tool does the work inside your browser using the JavaScript PDF engine loaded with the page, so the files you pick are read from your own disk and never sent to a server — which matters when the documents are contracts, bank statements or medical records.
How to use
- Choose or drag in the PDF files you want to combine.
- Drag the order into shape with the arrows — the first file becomes the first pages.
- Remove anything you picked by mistake, or sort every file by name in one click.
- Press Merge PDFs and the combined file downloads straight to your device.
What actually happens when PDFs are merged
A PDF stores its pages in a tree, and each page points at the fonts, images and colour profiles it needs. Merging rebuilds that tree in a new document and copies across every object each page depends on. Nothing is re-rendered or re-compressed, so text stays selectable and images keep their original quality.
Because resources are copied rather than shared, the merged file is roughly the sum of the originals. Two 3 MB reports produce a file near 6 MB even if they use the same fonts, since each copy of a font is carried along with its own pages. That is normal, and it is the price of a merge that does not touch quality.
Page size is preserved per page. A merged document can legitimately contain an A4 page followed by a US Letter page followed by a landscape scan — PDF has no rule that pages must match, and viewers handle the mix without complaint.
Things worth knowing before you merge
Password-protected files have to be unlocked first. A PDF encrypted for opening cannot be read without its password, so open it in your PDF reader, save an unprotected copy, and merge that.
Digital signatures do not survive. Any change to a signed PDF — merging included — invalidates the signature, because the signature covers the exact bytes of the original file. If a document must stay verifiably signed, keep it separate and send it alongside the merged file.
Interactive extras can be lost. Bookmarks, the outline panel and form fields belong to the document rather than to individual pages, so they are not carried into the new file. Page content, links inside the page and annotations attached to a page come across intact.
Merging efficiently
Name your files so they sort the way you want them read — 01-cover.pdf, 02-report.pdf, 03-appendix.pdf — then use Sort by name instead of dragging each one into place. This is far quicker for a twenty-file scan job than manual ordering.
If you only want part of a file in the result, split it first and merge the extract. Combining Split PDF and Merge PDF covers the common case of dropping a cover sheet or pulling three pages out of a long appendix.
Very large jobs are limited by memory rather than by any upload cap. Because everything is held in the browser tab, merging a few hundred megabytes at once can be slow on a phone; splitting the job into two merges and then combining the results is more reliable.
Frequently asked questions
Are my PDF files uploaded anywhere?
No. The merge runs in your browser with JavaScript, and the resulting file is written straight to your downloads folder. The documents never travel over the network, which is why the tool also works offline once the page has loaded.
Is there a limit on file size or number of files?
There is no imposed limit — the practical ceiling is your device memory, since every file is held in the tab while merging. Desktop browsers handle hundreds of megabytes comfortably; older phones will struggle sooner.
Will merging reduce the quality of my PDF?
No. Pages are copied object for object, not re-rendered or re-compressed, so text stays sharp and selectable and images are byte-identical to the originals.
Why can I not merge my password-protected PDF?
An encrypted PDF cannot be read without its password. Open it in your usual PDF reader, save an unprotected copy, then merge that copy.