Merge PDF
Combine PDFs into one file. Drag the pages into the order you want. The files never leave your computer, because there is nowhere to send them.
There is no upload
Every mainstream merge tool sends your documents to a server, does the work there, and promises to delete them within an hour or two. That promise is worth something, and it is also proof that the upload happened. Whatever is in the file has been on someone else's machine.
This does the work in the page. The file is opened by your own browser using its own file picker, the merge happens in memory, and the result is handed back to you. There is no upload endpoint on this site — not one that is unused, but none at all.
It is also why no progress bar appears anywhere here. Animating a transfer that never happens is theatre, and the habit is close to universal in this category.
Order is a drag, not a form field
Once the files are open you see every page as a thumbnail and you drag them into the order you want. Reordering does not need page numbers typed into a box, because you can see the pages.
This is possible precisely because nothing was uploaded — the document is already here, so rearranging it costs a repaint rather than a round trip.
What it is slow at, honestly
Merging is the heaviest operation in the set. Six hundred pages takes real seconds, because every page object is copied into a new document. A few dozen pages is instant; several hundred is a pause.
There is no size cap and no daily limit, which most of the hosted alternatives impose. iLovePDF caps its conversion tools at 15 MB. Sejda allows three tasks an hour and fifty pages. Smallpdf lets you do the work and then asks for money at the download.
What does not survive a merge
Pages carry across faithfully. The things attached to a document rather than to its pages do not always. Bookmarks pointing into the second file, named destinations, and document-level JavaScript are properties of the document you are merging from, and a merge builds a new document.
Form fields are the awkward case. Two files each containing a field called "name" cannot both keep it — a PDF form is a flat namespace, so one of them has to be renamed or dropped. If you are combining filled-in forms, flatten them first and you will keep the appearance without the collision.
Links between pages inside a single source file survive, because they are resolved against the page objects that came with them. Links pointing outside it do not.
Answers
Are my files uploaded?
No. This site has no upload endpoint. The merge runs in your browser and the file never leaves your computer.
Is there a size limit?
None imposed. Very large documents are limited by your own memory — a few hundred megabytes is the practical ceiling in a browser.
Can I reorder pages while merging?
Yes. Every page appears as a thumbnail and you drag them into the order you want before saving.