Attached are two screenshots from my Clara HD. The first shows a page with a heading and some footnotes. The second is zoomed in on that page 200%:
I didn't pay attention to the fact you were reading PDF. I would generally not recommend reading PDFs on any e-ink ereader. The screen size usually makes for a poor experience. As a rule, I find the display to be very good, but, the navigation if you need to zoom in on the page is terrible. Some of the ereaders will do PDF reflow, but the Kobo's do not.
To show you the ePub display, clicked the epub button on the site you linked and took the
first book shown. The following is a random page from it:
This is with the default font and without any other fiddling. The font is a little larger than I usually use, but it should show what the book looks like. And this is with the default font.
As to a font, the best way to do it is put it on the web somewhere and send me a PM with the link. If it is a freely downloadable font, the just post the link to were I can get it. Also, there aren't any options to choose a font when reading the PDF. I assume that means it is either using from inside the PDF, or only uses the system defaults.
And one last screenshot while I am at. This is the library list. It shows the titles in Greek in the list. The only thing not shown in that list is an example with series information:
