Merging PDFs without uploading them anywhere
Many free PDF mergers work by uploading your files to a server, processing them there, and sending back the result. A lot of people don't love putting a contract, a résumé, or a bank statement through that pipeline.
Merging in the browser keeps the file on your computer the whole time. Pick several PDFs, put them in the order you want, and if you only need part of one, specify a page range to pull out just that section before it gets stitched together.
Page ranges count from 1, the way people actually count
Type page ranges like 1-3,7 — counting starts at page 1, the way a person would count through the document, and commas chain multiple ranges together. Most software counts from 0 internally; you don't have to think about that here.
Why merging is trickier than it looks
Modern PDFs frequently compress their internal structure — cross-reference streams, object streams — in ways that trip up merge code written the naive way, silently dropping pages or corrupting the output. Rather than write that from scratch, this uses a well-tested open-source library instead. A slightly larger download beats quietly breaking someone's file.
What it won't do
It can't open a PDF that's password-protected. Remove the password first, then merge.
No caps, no trial, no surprise charge
Look at the cases Korea's Consumer Agency has taken in over trial periods that turned into automatic billing, and document- and video-editing tools top the list. Plenty of the well-known free PDF sites also cap you at a handful of files a day before asking for payment. There's no daily limit here, no trial period, and no billing at all — merge as many as you need, and it costs nothing either way.
Source: Smallpdf support · iLovePDF security notice · Korea Consumer Agency findings (Hankyung report)