extreme newbie how to use Sumatra pdf to save a word doc as a pdf

[dtilt1]

don't get how to use this program.
is not listed in the drop down choices in a word doc to save it as a pdf
I want to be able to choose between Adobe Acrobat and Sumatra pdf. I do not want to lose Adobe.
is this not possible?

tried to open a document in Sumatra and can't even see any Word docs to use

so I am totally not getting this