PDF Productivity

How to Merge PDF Files Into One Document

Last updated · By the PDFSolution team

Merging is the most common PDF task there is: an application form, three certificates and a covering letter need to arrive as one attachment. The mechanics are simple; the details that go wrong are order, orientation and size.

Ready to do it now? Open the tool this guide describes.

Merge PDF files

Step by step

  1. 1

    Gather every file first

    Add all the PDFs in one go so you can see the whole set before deciding the order.

  2. 2

    Drag them into reading order

    Cover letter, then main document, then appendices is the order most reviewers expect.

  3. 3

    Merge

    The combined PDF is built in your browser, copying pages without re-encoding them.

  4. 4

    Check and correct

    Scan the result for sideways pages and fix them with Rotate PDF.

Useful tips

  • Name files 01-, 02-, 03- before you start; the order then reads naturally when you add them.
  • If a single item is a photo rather than a PDF, convert it with JPG to PDF first.
  • Merged bundles are a good moment to add page numbers so reviewers can reference pages.

Common problems

One file will not merge
It is probably encrypted or damaged. Unlock it or run Repair PDF, then try again.
The merged file is huge
Compress it afterwards, or compress the largest source document before merging.

Frequently asked questions

Does merging change quality?
No, pages are copied as-is.
Can I merge different page sizes?
Yes. Each page keeps its own size, so A4 and Letter pages can sit in the same document.
Can I merge on a phone?
Yes, though very large files may be limited by the phone's memory.

Related guides

  • How to Compress a PDF OnlineWhy PDFs get big, which compression level to choose, and how to get a file under an email limit without ruining it.
  • How to Edit a PDFPDFs were designed to be final. Here is what can realistically be edited, and the fastest route for each kind of change.
  • How to Extract Pages From a PDFSend only the pages that matter, instead of a 200-page document with a note saying 'see page 47'.