You could try dragging the .pdb file into
SUPER to see if it can convert it. It's not listed at one of the myriad of files it plays well with, but, for free, it may be worth the shot.
OTOH, if it's not too personal in nature, you can e-mail your .pdb to me. I'd be happy to see if I can convert it with MY version of SUPER.
Download
SUPER
Randy