Merging PDFs is one of those tasks that feels like it should be built into every operating system but somehow isn't. Whether you're combining scanned documents, assembling a report from sections, or joining a cover letter with a résumé, the process is straightforward.
The simplest approach is a browser-based tool like fwip. Open the merge tool, drop your PDF files in the order you want them, and download the combined result. Everything happens locally in your browser — no upload, no account, no watermark. You can reorder pages by dragging before merging.
On Mac, Preview has a hidden merge feature. Open the first PDF, show the sidebar (View → Thumbnails), then drag additional PDF files into the sidebar at the position you want. Save with File → Export as PDF. It's clunky but functional.
On Windows, there's no built-in option. Adobe Acrobat (paid) is the standard, but for free merging, PDFsam Basic is a solid desktop alternative. It's open-source and handles merge, split, and rotate operations.
For command-line users, Ghostscript and qpdf both merge PDFs reliably. The qpdf command is simpler: `qpdf --empty --pages file1.pdf file2.pdf -- output.pdf`.