How to Merge PDF Files

Combine several PDFs into one file in your browser. Learn how to set the order, prepare pages, handle passwords and forms, and finish the merged document.

What merging a PDF actually does

Merging takes the pages from several PDF files and copies them, in the order you choose, into a brand-new document. Nothing is converted or re-rendered: text stays text, vector graphics stay sharp and images keep their original quality. That makes merging very different from printing several files to a new PDF, which can flatten content and lose features.

Typical reasons to merge include sending a single application packet instead of a pile of attachments, combining scanned receipts for an expense report, assembling chapters into one manuscript or attaching signed pages to the rest of a contract. A single file is easier for the recipient to read, print and archive, and it removes any doubt about the intended order.

Prepare your files before you merge

A few minutes of preparation saves you from fixing the merged document afterwards.

• Name your files so you can recognize them in the list, for example 01-cover.pdf, 02-letter.pdf and 03-references.pdf.
• Remove pages you do not want with Delete PDF pages, or keep only the pages you need with Extract PDF pages.
• Fix sideways scans with Rotate PDF so every page reads the right way up.
• Note the passwords of any protected files. You need them to open the files, and the merged result is saved without a password.
• Check sizes: Merge PDF accepts up to 12 files of up to 50 MB each, with 100 MB and 1,000 pages in total.

How to merge PDFs step by step

1. Open Merge PDF and drop your files onto the page, or select Choose PDF and pick several files at once.
2. If a file is password-protected, enter its password in the PDF password field before adding it, then select Open PDF.
3. Review the list. Each card shows the first page, the file name and the number of pages, numbered in merge order.
4. Use the up and down arrows on each card to change the order, the remove button to drop a file, and Add PDFs to include more.
5. Select Apply. When processing finishes, preview the result and download merged.pdf.

The whole process runs in your browser with the pdf-lib library, so the files are never uploaded. Large merges may take a few seconds on older devices, and you can cancel at any time.

Getting the page order right

Merge PDF keeps the internal page order of every file and joins the files one after another. If you need to interleave pages, for example placing a signed page in the middle of another document, merge first and then open the result in Reorder PDF pages. There you can drag thumbnails or use the arrow buttons to put every page exactly where it belongs.

Double-sided paper scanned in two passes is a common case. Scan the front sides as one file and the back sides as another, merge them, then move the pages into front, back, front, back order with Reorder PDF pages.

What happens to forms, bookmarks and properties

Page content, annotations and interactive AcroForm fields are copied with their pages. Because two files can contain fields with the same name, which would otherwise link them together, the tool prefixes field names with the file number, such as File1_ and File2_, so every field stays independent and editable. Files with XFA forms are not supported and are reported before merging.

Some document-level features belong to a single file and do not carry across. The bookmark outline of each source file is not included, links that jump to a page in another document may stop working, and the title and author of the original files are not kept. If any source file was digitally signed, those signatures do not carry over into the new document either, because it is a different file.

Finishing the merged document

After merging, a few optional steps make the result more professional:

• Add page numbers with Add page numbers so readers can refer to specific pages of the combined file.
• Set a title, author, subject and keywords with the PDF metadata editor. Many PDF readers show the title in the window bar instead of the file name.
• Reduce the size with Compress PDF if the result is too large to email.
• Encrypt the file with Protect PDF as the very last step if it contains personal or confidential information.

Frequently asked questions

Is there a limit on how many PDFs I can merge?

You can merge up to 12 PDFs at once, with 1,000 pages in total. To combine more, merge them in groups and then merge the results.

Will merging reduce the quality of my PDFs?

No. Pages are copied as they are, without re-rendering, so text, images and vector graphics keep their original quality.

Can I merge PDFs on my phone?

Yes. The tool works in current mobile browsers. Very large files need more memory, so on older phones merge fewer or smaller files at a time.