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How to merge PDFs into one file

Merging combines two or more PDF files into a single document, in the order you choose. It is one of the most common PDF tasks — and one of the easiest to get subtly wrong, usually because of page order or a forgotten page.

When merging is the right move

Merge when a single submission needs several documents in one file: an application form plus its supporting certificates, a set of monthly bills for one expense claim, or chapters of a report that were scanned separately. One file is easier for the receiver to store, forward and print than five attachments, and it removes the risk that one attachment gets missed.

Do not merge when the receiver asked for separate files, or when different pages need different handling — for example, if only one certificate needs to be shared and the rest of the file is private. In that case, extract just the pages you need instead (see our split guide).

Step by step

1. Open the PDF Merge tool and drop your PDF files in, or click to browse and select several at once.
2. Check the order. Use the up and down buttons to move files until the order matches the order a reader should see — cover page first, then the main document, then annexures.
3. Optionally type an output filename, for example application-with-certificates.pdf. A clear name helps the receiver more than merged.pdf does.
4. Click Merge, wait for the result, and download the combined file.
5. Before sending, open the merged file and scroll through it once: check the first page, the last page, and every join between two original files. A missing page is much easier to catch now than after submission.

What merging does not do

• It does not reduce file size in any meaningful way. The merged file is roughly the sum of the originals. If you need a smaller file, see how to make a PDF smaller.
• It does not edit text, fix a scanned page, or make a scanned image searchable. Merging only reorders and joins pages.
• It does not remove passwords. A password-protected PDF must be unlocked first, then merged.
• It does not change page size or orientation. A landscape page stays landscape inside the merged file.

Size and device limits, honestly

This tool runs entirely in your browser, so your files are never uploaded anywhere — but the work happens on your device. As a practical rule, totals under about 100 MB work smoothly on most phones and laptops. Above that, an older phone may slow down or run out of memory. If a very large merge fails, try merging in two batches and then merging the two results, or do it on a laptop instead of a phone.

Common mistakes

• Wrong order: files added in the order they were selected, not the order you intended. Always re-check the list before merging.
• Duplicate pages: the same file added twice, usually by dragging a folder and a file together. The file list shows every file — scan it before clicking Merge.
• Sending without opening: a merge can succeed while one source file was blank or corrupt. Opening the result once catches this.

Frequently asked questions