I attempted to use potrace but part of the image is gone after the
conversion:
https://drive.google.com/open?id=0BweRamx9lXSLZjZNQzdYZHB4djA
What am I doing wrong?

These are the commands I entered to due the conversion:

 convert watermark3.jpg watermark3.ppm
 potrace -s watermark3.ppm -o watermark3.svg

I looked into the manpage and it seems that you are telling it the *.ppm is
a SVG file but maybe you are telling it you want to convert the ppm to
svg.... I don't know.
-- 
:-)~MIKE~(-: