Pdf version can be read offline after you downloaded it, and the regular digital version has to be read online.
Also PDF version is a replica of the printed newspaper and therefore preserves the newspaper format, but it's tiresome to read on mobile devices because you need to zoom in and out a lot.
The digital version has a breaking news section and this is obviously unavailable on the pdf version.
Each has its pros and cons, but for ease of reading, I personally prefer the non-pdf version.