If you can root the Nook, you can install 3rd party pdf reading apps.
Kindle software is extremely limited. I imagine it's very bad for reading pdf.
But any 6" e-reader is a pain for reading pdf. Though I do it on a rooted Nook ST sometimes with okay results.
However, there is a program called k2pdfopt that changes the size and format of pdf files to work better on a 6" screen. It will work for any e-reader.
Here it is:
https://www.mobileread.com/forums/sho...d.php?t=144711