Merge PDF

How Merge PDF works

Combine several PDFs into one document in the order you choose. Pages, bookmarks and text stay intact. Everything happens inside this page: the tool reads your input, runs the calculation or conversion locally, and hands the result back to you. Nothing is transmitted, because there is no backend to transmit it to.

That design choice is deliberate. Most free tool sites upload your files to a server, process them there, and quietly keep a copy. Toolcin cannot do that — the site is a set of static files. If your connection dropped the moment the page finished loading, every tool would still work.

How the merge actually works

The tool loads each PDF, copies every page from it into a new document, and saves that document as one file. Pages are appended in the order the files appear in the list, which is the order you selected them — re-select in a different order if you want a different result.

Everything happens with pdf-lib running inside the tab. The files are read as bytes, combined in memory, and downloaded directly. There is no upload step, so a contract or a medical scan never leaves your machine.

What survives the merge, and what does not

Page content survives: text, images, vector graphics and the page size of each original page. A4 and Letter pages can sit in the same output file, each keeping its own dimensions.

Document-level extras do not. Bookmarks and outlines, form fields, JavaScript actions and document metadata such as the author name are not carried across, because the new document is assembled page by page rather than by concatenating the original files. If a bookmarked PDF is important, keep the originals alongside the merged copy.

Password-protected and damaged files

A PDF that opens only with a password cannot be merged reliably. The tool will try to ignore the encryption flag, which sometimes produces a file whose pages are unreadable — that is a limitation of the library, not a bug you can work around from here.

If a merge fails, the usual causes are a corrupted download, a file that is actually an image renamed to .pdf, or a PDF with incremental updates that confuse the parser. Open the suspect file in a normal reader first; if it opens there and still fails here, send the file name in a report.

Order, page ranges and file size

There is no page-range picker in the merge step: whole files go in. If you need pages 3–7 of one document and 1–2 of another, split each first and merge the pieces. Two tools, one predictable result.

The merged file is roughly the sum of the inputs, because pages are copied rather than re-compressed. Merging ten 2 MB scans gives you about 20 MB. If that is too large to email, compress the images inside each PDF before merging, since merging itself will not shrink anything.

Good to know

• Works offline once loaded, including on flights and in locked-down networks.
• No file size limit beyond your device's own memory.
• Free to use, with no account and no usage counter.
• Results are produced locally, so they are not logged or shared with anyone.

Questions