About this tool
A contract body, its annex and the signature page; ten scanned receipts that have to go in as one attachment; a report plus the slides that go with it. This page joins PDF files into a single PDF without sending them anywhere. Drop the files in, drag them into order (or sort them by name — 2.pdf lands before 10.pdf), and, for any file, type a page range such as 1-3, 7, 10- to take only those pages. Each file shows its name, page count, size and whether it is encrypted, so you can see what you are about to join before you join it.
Nothing is uploaded, and nothing extra is written
The merge runs in JavaScript inside this tab. There is no server behind the page, so the files cannot leave your machine — turn the network off and it still works. The output is built as a fresh document with no Document Information Dictionary at all: no Author, no Producer, no creation or modification date, and nothing naming the tool or your computer; per-page XMP metadata is dropped too. That covers document information only: comments and other annotations are page content, so they are kept along with the name of whoever wrote them — delete them in your PDF reader first if they should not travel. Before the download is offered the merged file is loaded again and its page count is checked against the sum of the pages you selected; if they disagree you get an error, not a file. If you want to see or strip what an existing PDF says about itself, the Remove PDF Metadata tool reads those fields.
What a merge can lose
Merging copies pages from one document into another, and some things live outside the pages. Bookmarks (the outline) may not come across. Links that jump to another page, and table-of-contents links, may stop working because they point at page objects in the original file. Form fields may show but no longer be fillable. Accessibility tags (the Tagged PDF structure tree) may not be preserved. One thing is certain rather than possible: a digital signature will no longer verify, because merging changes the bytes it signed — that is true of every merge tool, not a fault of this one.
Password-protected PDFs are listed, marked as encrypted and left out of the merge; the other files still merge normally. This page does not ask for, guess or remove passwords. Once the download is offered, the merged PDF is an ordinary file: open it, print it, attach it, or drop it back on this page to join it with something else.