Merging PDFs is one of the most common tasks people need from a PDF tool. You might have scanned a multi-page form as separate pages, received several invoices that need to go in one email, or accumulated chapters of a document in different files. Merging combines them all into one clean PDF.
How to merge PDFs with PDF99
The fastest way is to use our free Merge PDF tool. Here's exactly what to do:
- Go to the Merge PDF page and click Choose PDF files (or drag multiple files onto the page at once).
- Add all the files you want to combine. You can add them in any order — you'll be able to rearrange them.
- Check the order in the thumbnail area. The files will be merged from top-left to bottom-right.
- Click Merge PDFs and download your combined document.
The whole process takes under a minute for most people.
Does merging PDFs lose quality?
No. PDF99's merge tool uses PDF-lib, which copies pages from source files directly into the merged document. There's no re-rendering, no compression, no quality change whatsoever. The merged PDF contains exactly the same content as the originals.
What if my PDFs have different page sizes?
That's fine. PDF-lib preserves each page at its original size and orientation. A merged PDF can contain A4 and A5 and Letter-sized pages — each page stays exactly as it was in the original file.
Is there a limit on how many PDFs I can merge?
PDF99 has no limit. You can merge two files or two hundred. The only practical constraint is your browser's memory — very large PDFs with many high-resolution images may slow things down on older hardware.
Alternatives if the online tool doesn't work for your use case
For very large batch merges, a desktop tool like LibreOffice Draw or the free Ghostscript command-line utility can be more reliable. For developer use cases, the pdf-lib npm package provides the same functionality programmatically.