Sure! You must install JB Patch:
https://www.mobileread.com/forums/sho...d.php?t=175512
It features a patch to modify margins in both pdf and not pdf view:
https://wiki.mobileread.com/wiki/JBPa...Reader_Margins
I've reduced them too, even if 0 margin would be too small in my opinion.
But pay attention: this patch requires the first version of Kindle Paperwhite (the now-selling new one is NOT supported!) and firmware 5.3.4! So you could have to downgrade/upgrade it