I have a epub with a bunch of formulas as jpg files. In the epub they are super crisp, but during epub to pdf conversion all the images become blurry, I'd imagine they are jpg compressed. How can this be fixed?
You should look for a Calibre option for JPG files that does not cause them to lose quality. Look through the manual.
I know Adobe Distiller has options to keep high-quality JPG files. Does Calibre call Distiller or does it have it's own PDF maker?