Hi, Alleyoop. Yes, you can add other fonts to the 950.
One method is to install PRS+ which is an enhanced firmware (not sponsored by Sony and created by Sony ereader users to get around what they see as shortcomings in the official firmware). Sorry, I don't have PRS+ installed so I can't offer much guidance on this method. It works with DRM'ed files though. However, lots of people on the forum do have PRS+ installed, and other people can help you.
Another method is to use software like calibre to modify the book CSS to call out your preferred fonts (or Sigil is another software option too). Here is a link to a post which explains how to use this method. Scroll down to the bottom of the post and see the attached PDF. One note is that your books can't have DRM for this method. It's how I change fonts on my 950. My personal favorite is Lexia DaMa. There are several threads on what fonts people like if you do a search within the forum.
https://www.mobileread.com/forums/sho...04&postcount=1
Hope that helps!