Several forum members from both the English and German sub-forum have been asking about the annotation capabilities of the pocketbooks 603 / 903 for some time now.
However, as pocketbook team members hardly seem to react, I have come to the believe that taking notes (i.e. writing down your own thoughts via stylus, virtual keyboard or bluetooth keyboard) is not in the capability of the 903
(though i'd
love to be taught otherwise).
The note taking function that pocketbook advertises on their homepage seems to be restricted to copying segments from already existing documents for later referral.
In the German sub-forum, it has been mentioned that the 903 does not support handwriting recognition (yet).
However, it seems another option might be to scribble your notes and save them (possibly) as a picture file.
Though I do understand that functionality of the new devices is limited by the use of eINK technology, I sincerely do believe that Pockebook team should let their customers know about possible restrictions, as there seem to be quite a few forum members who took a leap of faith and ordered the 903 because of its supposed annotation capabilities.