Merge multiple PDFs into one file
Join several PDF documents into one file, in the order you choose, without any of them leaving your device.
What it does
ConvUp opens each PDF in your browser memory, copies its pages with pdf-lib and writes a new document. Pages are not rasterized, so text, links and the original quality are preserved.
You can reorder the list before merging, mix documents from different sources and download a single PDF ready to send, archive or print.
How to use it
- Open Merge PDF in ConvUp.
- Drag two or more PDF files or pick them from your file manager.
- Reorder the list with the arrows until the files are in the right order.
- Press “Merge PDF” and download the resulting document.
Why ConvUp
No uploads
Files are processed on your computer. There is no conversion server or remote copy.
No watermarks
The resulting PDF has no logos, stamps or extra pages.
No account
You do not need to sign up or pay to download the result.
Merging PDFs without uploading them: what actually changes
Most online converters receive your files, merge them on their server and send the result back. Here there is no conversion server: the browser opens each PDF with pdf-lib, copies the pages and builds the new document in your machine's memory. Open the developer tools (F12), switch to Network and merge your files — no request will carry their content.
That matters for documents that should not leave home: contracts, payslips, medical reports, deeds or ID scans. The page itself is downloaded once, but the heavy work happens locally and the result exists only on your device until you decide to save it.
When a PDF refuses to merge
Password-protected files cannot be read: open them in your reader, remove the protection and try again. Corrupted or truncated PDFs usually fail on load; open them in a viewer and save them again as PDF to rebuild the structure.
Mind what is kept, too. Pages are copied as they are, so text and images keep their original quality, but bookmarks, fillable forms and digital signatures are not carried over: a digital signature stops being valid the moment the file changes. The final size is roughly the sum of the inputs, because nothing is recompressed.
Frequently asked questions
Are my PDFs uploaded to a server?
No. ConvUp has no conversion backend: your files are read and combined in your browser memory. You can check it in DevTools → Network while processing the document.
How many PDFs can I merge?
Up to 40 files, with a maximum of 300 MB per file and 700 MB in total. The limits keep the browser from running out of memory.
Is quality lost when merging?
No content is recompressed. Pages are copied into the new document, so text and images keep their original quality.
Does it work on mobile?
Yes, in modern browsers on Android and iOS. For very large documents, a computer has more memory available.