The fastest safe way: install PDFsam Basic (free, open source), drag your PDFs into its Merge module, click Run. Everything happens on your machine. Here is that walkthrough, two alternatives, and why the "free" online mergers are the one option to avoid.
Think about what people merge: invoices, contracts, medical records, tax documents, scanned IDs. The online mergers ask you to upload exactly those files to a server you know nothing about, run by a company whose business model you cannot see. Some are honest and delete promptly. Some are monetizing you in ways the landing page does not mention. You cannot tell which is which, so the safe default is the same one this whole site is built on: documents stay local. Happily, the local options are free too.
PDF24 Creator (Windows): a free toolbox whose merge tool also works offline, with a friendlier drag-and-drop layout if PDFsam feels utilitarian. macOS Preview: already on every Mac. Open the first PDF, show the thumbnail sidebar, and drag the other PDFs into it, then export. No install at all.
People append "reddit" to searches like "free pdf merger" because they are tired of SEO-spam tool sites, and fair enough. The community consensus has been stable for years: PDFsam Basic for straight merging, PDF24 for a broader free toolbox, Stirling PDF if you are technical enough to self-host, and a persistent warning against uploading sensitive documents to online tools. Which is, word for word, the advice on this page.
No Bloat PDF does not merge files, and that is deliberate: every feature bolted onto a viewer is a step toward the bloated readers it exists to replace. It is the other half of this workflow: the free 4.6 MB reader that opens the merged result instantly, with tabs, search, annotations, and signatures, and zero network calls. Merge with PDFsam, read with No Bloat PDF, and nothing in the chain ever saw your documents but you.
Version 1.0.0 · Windows 10/11 (x64) · 4.6 MB · free forever
Signed, 4.6 MB, zero telemetry. Free forever.