How to merge multiple PDFs into one file

Published 14 August 2026 · 5 min read

Combining scanned receipts into one file for an expense report, attaching a cover letter to a resume, stitching several chapters of a report together before sending it, merging PDFs is one of those small tasks that comes up constantly. It's also one people often solve badly, by emailing five separate attachments and letting the recipient sort them out. Here's how to do it properly, and what actually happens to your files when you do.

Why merge instead of sending files separately

A single combined file is easier for the person on the other end: one thing to download, one thing to print, one thing to file away. It also guarantees the reading order, five separate attachments can get opened, printed, or reviewed in any order, while a merged PDF reads top to bottom exactly as you arranged it.

Step by step

Open the Merge PDF tool.
Drop in two or more PDF files, or click to choose them from your device.
Use the ↑ / ↓ buttons next to each file to put them in the order you want the merged document to read.
Click "Merge PDFs." The combined file downloads immediately.

What actually happens to the content

Merging doesn't re-render or re-compress anything, each page is copied into the new file exactly as it existed in the source PDF, using the open-source pdf-lib library. Text stays selectable if it was selectable before, images stay at their original resolution, and the final file size is roughly the sum of the source files (there's a small amount of shared overhead, so it's often slightly less than a simple sum, not more).

One thing that doesn't carry over: if any of your source PDFs have a bookmarks panel or table-of-contents outline (the clickable sidebar some PDF readers show for jumping between sections), that navigation structure isn't preserved in the merged file, only the page content itself is. For most everyday documents that's not something you'll notice, but it's worth knowing if you're merging something like a long reference manual that relies on its bookmarks.

A quick example

Say you're filing an expense report: three photos of receipts saved as PDFs from your phone's scanner app, plus a cover sheet you typed up separately. Add all four to the tool, drag the cover sheet to the top of the list with the ↑ button, check that the receipts are in a sensible order underneath it, and merge. You get one file to attach to the email instead of four, and the person reading it doesn't have to guess which receipt is which by opening each attachment individually.

Where this hits limits

Password-protected PDFs can't be merged directly. The tool needs to read each page to copy it, and an encrypted file can't be read without the password first, that's a limitation worth knowing about rather than discovering mid-task.
Order doesn't fix itself. Files merge in exactly the order shown in the list. There's no automatic sort by filename or date, check the order before you click merge.
A large combined file stays large. If the result feels too big to email, that's a separate problem, run it through Compress PDF afterward rather than expecting merging to shrink anything.

Ready to combine your files?

Open Merge PDF

Frequently asked questions

Can I merge password-protected PDFs?

Not currently with this tool. An encrypted PDF can't be read without its password first, and password removal isn't something this tool does yet. You'd need to remove the password with another tool before merging.

Is there a limit to how many files I can merge?

No artificial limit. Since everything runs on your device rather than a server, the practical ceiling is your browser's available memory, for a handful of typical documents that's not something you'll run into.

Will merging reduce the quality of my PDFs?

No. Pages are copied into the new file exactly as they were, nothing is re-rendered or re-compressed in the process.