Comment by omnimus

There are many powerful native pdf tools but they are usually paid and you have to install them. Preview is ok but its only on mac. Preview also has only some of the features.

These online converters are immensely popular for a reason. They also used to do everything serverside and had ads all around which is obviously terrible security wise. So having WASM versions is much better.

Since these are link away they are easy to send and save. I help self-host a podcast and you need very particular settings for the export of the audio file. Instead of cooking up some automated solution, editors have bookmark of this https://ffmpeg-online.vercel.app/ with all the ffmpeg settings correctly selected and they can do the final file themselves for both their preview and production.

Compare that to having multiple people with multiple platforms having to install and learn to use some gui app.