Why merging locally matters here
Merging PDFs is the single most common thing people need to do with them — combining a signed contract with its annexes, assembling receipts for an expense claim, putting a scanned application back together.
It is also, very often, the most sensitive. Those documents carry names, addresses, bank details, medical information, salary figures and signatures. Every mainstream online merge tool asks you to upload all of it to their servers.
Rasp does the work in your browser. The files are read from disk into memory, combined, and handed back as a download. Nothing is transmitted, so there is nothing to be retained, indexed, or exposed in someone else’s breach.
Is it safe to merge PDFs online?
The honest answer is: it depends on the site, and you usually cannot tell from the outside.
An uploading tool may be perfectly well run. But the file has left your machine, and from that point you are relying on their retention policy, their access controls and their security. For a restaurant menu that is fine. For a mortgage application it is a decision worth making deliberately.
The distinguishing feature here is that the claim is measurable rather than stated. The Uploaded readout beside the result is wired to this page’s own outbound network calls, and reports what actually left the browser. On a successful merge it reads 0 B.
What carries across, and what may not
Page content, images, links and annotations are preserved. Each source document’s pages are copied into the new file in full, without re-compression, so nothing is degraded.
Two things to watch. Interactive form fields and bookmarks are properties of a document as a whole rather than of individual pages, so they may not survive a merge. If your documents contain fillable forms you still need to work, check the result before discarding the originals.
Password-protected files
A PDF that restricts editing or printing will usually merge without trouble. A PDF that requires a password simply to open cannot be read at all without it, and will report an error.
Remove the password in your PDF reader first, then merge.
How large will the result be?
About the sum of its parts. Merging does not compress anything, so five 2 MB documents produce a file of roughly 10 MB.
Questions
- Is it safe to merge PDFs online?
- It depends entirely on whether the site uploads them, and most do. Your document is transmitted to a server, processed there, and retained for some period. That matters because merged PDFs are usually the sensitive ones — contracts, statements, medical records. This page does not upload anything: the merge runs in your browser, and the Uploaded readout measures the page's own outbound traffic so you can verify it.
- Is there a limit on how many PDFs I can merge?
- No limit is imposed, because no server is doing the work. Your device's memory is the only ceiling. Merging dozens of ordinary documents is comfortable on a laptop.
- How do I control the page order?
- Files merge top to bottom in the list. Use the arrows beside each file to move it up or down before merging, and the cross to remove one you added by mistake.
- Are password-protected PDFs supported?
- Documents that merely restrict editing or printing will usually merge. Documents that require a password to open cannot be read without that password and will fail. Remove the password in your PDF reader first, then merge.
- Are form fields, links and bookmarks kept?
- Page content, images, links and annotations are carried across. Interactive form fields and bookmarks may not survive, because they belong to the document as a whole rather than to individual pages. If your documents contain fillable forms you need to keep working, check the result before discarding the originals.
- Will there be a watermark?
- No. Nothing is stamped onto the pages and there is no paid tier that removes anything.
- Do I need to create an account?
- No. There is no account system, because there is no server holding files that would need one.
- Does merging reduce quality or re-compress anything?
- No. Pages are copied into the new document as they are. Images are not re-encoded and text is not rasterised.
- How big will the merged file be?
- Roughly the sum of the inputs. Merging does not compress, so combining five 2 MB documents produces a file of around 10 MB.
- Can I merge a PDF with an image?
- Convert the image to a PDF first using the JPG to PDF or PNG to PDF page, then merge the two documents here.
- Does it work offline?
- Often, but it is not guaranteed. The page is cached by your browser after first use, so later merges may work with no connection. There is no service worker here, so treat it as a convenience rather than a promise.
- Are my original files modified?
- Never. The files on your disk are read into memory and left exactly as they were. The merged document is a new file.