How to Merge PDF Files into One Document
Merging PDF files combines multiple separate PDF documents into a single file, in any order you choose. It takes under a minute online and requires no software installation.
Why merge PDF files?
Merging PDFs is useful when you need to submit multiple documents as a single file — such as a cover letter with a CV, a contract with its appendices, or multiple scanned pages from a flatbed scanner.
Merging also simplifies file management: instead of tracking dozens of separate files, you keep one combined document that's easier to email, share, and archive.
How to merge PDF files online (step by step)
1. Go to the WhiskFile Merge PDF tool.
2. Click "Choose files" or drag and drop your PDFs onto the upload zone. You can add up to 20 files at once on the free plan.
3. Arrange the files in the order you want them to appear in the final document. Drag each file card to reposition it.
4. Click "Merge PDF". Processing takes a few seconds per file.
5. Download the merged PDF. The output file will contain all pages from all input files in the order you specified.
Can I merge PDFs and images together?
Yes. WhiskFile automatically converts JPG, PNG, and TIFF images to PDF before merging, so you can mix document formats in a single merge operation. Upload your PDFs and images together and they will be combined in the order you arrange them.
What happens to hyperlinks and bookmarks when merging?
Hyperlinks within the individual PDFs are preserved in the merged output. Bookmarks (table of contents entries) from the original files are also preserved.
Cross-document links (links from one input file that point to a page in another input file) will not automatically update to the new combined page numbers. If cross-document links are important, use the WhiskFile Create PDF Bookmarks tool after merging to rebuild the navigation structure.
Tips for a clean merge
Make sure all files have the same page size (A4 or Letter) before merging, or the result may have inconsistent page dimensions. Use the WhiskFile Resize PDF tool to standardize page sizes first.
If file size is a concern after merging, run the result through the Compress PDF tool. Merging itself does not increase file size beyond the sum of the inputs, but compressing the output can reduce it further.
Frequently asked questions
- How many PDF files can I merge at once?
- On the free plan you can merge up to 20 files at once. Pro plan users have no limit on the number of files per merge.
- Will merging PDFs reduce quality?
- No. Merging is a lossless operation — the original page content (text, images, vector graphics) is preserved exactly. Only file metadata may be slightly modified.
- Can I merge scanned PDFs?
- Yes. Scanned PDFs merge just like any other PDF. If you need the resulting document to be searchable, run it through the OCR PDF tool after merging.
- Can I merge password-protected PDFs?
- No. Remove the passwords first using the Unlock PDF tool, then merge. Re-apply protection afterward with the Protect PDF tool if needed.
- Is there a file size limit for merging PDFs?
- Individual files can be up to 50 MB on the free plan (500 MB on Pro). There is no limit on the total combined size of the merged output.