Merge PDF
Combine multiple PDFs into one file.
How to merge pdf
- Add your PDF files
Drop your PDFs onto the page or click 'Select files'. You can add as many as you need.
- Reorder if needed
Drag the files up or down to set the order they will appear in the final document.
- Merge and download
Click 'Merge PDFs'. Your combined file is ready in seconds — click Download to save it.
Merging PDFs is one of the most common document tasks — assembling a report from separate chapters, combining scanned pages, or gathering invoices into a single file. OnlinePDF handles it entirely in your browser: no upload, no waiting for a server, and no size limit imposed by a pricing plan.
How to merge PDF files
Drop your files onto the tool, arrange them in the right order by dragging, and click Merge PDFs. The result is a single PDF containing all pages from each source file, in the order you chose.
Processing happens using WebAssembly compiled from the same open-source library that powers desktop PDF software. Your files are read into memory, combined, and handed back to you — nothing is ever sent anywhere.
Tips for a clean merge
If you are assembling a multi-chapter document, make sure each source PDF starts on the right page (odd for right-hand pages if you plan to print double-sided). For scanned documents, check that all pages are oriented the same way before merging — use the Rotate PDF tool to fix any that are upside down.
Frequently asked questions
- How many PDFs can I merge at once?
- There is no hard limit on the number of files. Practical limits depend on your device memory — on most computers you can comfortably merge dozens of files totalling several hundred megabytes.
- Will the merge preserve bookmarks and links?
- Internal links within each document are preserved. Cross-document bookmarks are not automatically merged, as each source file has its own structure.
- Can I merge password-protected PDFs?
- No. Remove the password from each PDF first using your PDF viewer, then merge the unlocked files here.
- Does the order of files matter?
- Yes — the files are combined in the order you see them in the list. Drag to reorder before clicking Merge.
- Is there a file size limit?
- Up to 100 MB total on desktop and 50 MB on mobile. Processing happens in your browser, so available memory is the real constraint.
Tips
- Name your files with a number prefix (01-intro.pdf, 02-chapter.pdf) before uploading so they sort in the right order automatically.
- If the merged file is very large, try using the Compress PDF tool afterwards to reduce its size.
- You can use Extract Pages first to pull only the pages you need from a large document before merging.