I disagree on that. I think that the main value of this kind of tools is "no installation required".

There are already free PDF editors that can be downloaded and installed once forever. What I used most is Libreoffice Draw: it imports a PDF, edit it as if it were a file in its own format, export as PDF again. It's not the only choice. Firefox has had a vanilla PDF editor since last year: download a PDF or drag one inside the browser window, edit it, save it. It's enough to add a PNG of my signature and fill out forms.