What merging a PDF actually does
When you merge PDFs, you're combining the pages from multiple separate documents into a single PDF file. The result is one file that opens and scrolls through just like any other PDF. The original files are not changed — you get a new merged document as the output.
This is different from attaching PDFs together in an email or zipping them. A merged PDF is a single coherent document: one file, one table of contents (if you add one), one download link to share.
The order of pages in the output follows the order you place the files. If you need page 3 of file B to come before page 1 of file A, you can split and reorder before merging.
- Combine contracts and their addenda
- Join multi-page scans into one document
- Assemble reports from multiple PDF exports
- Package invoices or receipts into one file
How to merge PDFs on Irreva
Go to the Merge PDF tool. Click the upload area or drag your PDF files into it. You can add as many files as you need. Once they appear in the list, drag them into the order you want — the first file in the list becomes the first set of pages in the output.
When the order looks right, click Merge. The tool combines the files using pdf-lib, a JavaScript PDF library that runs entirely in your browser. Your documents are never sent to any server. The merged PDF downloads directly to your device.
The whole process takes a few seconds for most documents. Very large PDFs with lots of high-resolution images may take a little longer depending on your device's speed.
Tips for better merged PDFs
If your source PDFs have different page sizes — say, some A4 and some letter — the merged document will keep each page at its original size. This is usually fine for digital use but can look inconsistent when printed. If uniformity matters, consider converting all pages to the same size first.
If any of your source PDFs are password protected, you'll need to unlock them first before merging. Use the PDF Unlock tool to remove the password, then merge.
After merging, you can use Add Page Numbers to number the pages sequentially across the combined document, which is useful for longer reports or legal documents.
Troubleshooting common issues
If a file doesn't appear or the tool reports an error, the PDF may be corrupted or use a non-standard encryption that the library can't read. Try opening the file in a PDF viewer first to confirm it works.
If the merged file is much larger than expected, the source PDFs likely contain uncompressed images. After merging, run the output through the Compress PDF tool to reduce the size.
If pages appear in the wrong order, drag the file tiles in the upload area to reorder them before clicking Merge. The order in the list is the order in the output.