What is in here, and what is not
Three kinds of article. A how-to walks through one job from the file you have to the file you need. A comparison sets two approaches beside each other and says where each one genuinely wins, including where this site's approach is the weaker one. A guide explains how something works, for the times when understanding the mechanism is what actually solves the problem.
What is deliberately absent is any article about a tool that is not built. Three PDF features — password protection, unlocking and optical character recognition — are on the roadmap and are marked as such rather than described as though they work. Writing a guide to one of them would waste the single visit somebody with that job to do was ever going to give this site.
Every article ends with the tools it used, so you can go straight from reading about the job to doing it. As with everything else here, the tools run inside your browser and your files are never uploaded.