Found some image/pdf conversion tools that run in the browser.

https://tools.filefolder.org/

They do image conversion, resizing, and some pdf manipulation. I convert %#}~%?} webp to jpg or png all day long (they don't render on DU) and so on.

I haven't tried them all, but if you find that they work for you, I'll post this in photography. Phones typically require separate apps to do this stuff.

Real computers come with more versatile apps installed or easily downloadable, but don't fit in your pocket.