Looks as Aura has it's own quirks in addition to nice screen.
Check out
this review.
They state:
1. About pdf:
"None of the usual on-screen features work either. So there's no way to add notes, or highlights, and the only way to reference the dictionary is to type the word in manually".
2. Conclusion:
"Ultimately I think the Kobo Aura HD is more suited for ereader/E Ink aficionados rather than casual readers just getting into ereading for the first time. For one, users need to be familiar with converting ePubs and tweaking CSS settings with Calibre in order to avoid 2" of wasted space at the bottom of pages with most sideloaded ePubs"