How can I change the size of a pdf source file, or, convert it to Word?
A lot depends on the form of the PDF. Is it graphics, a scan of a text file, pure text, or other? What version of Acrobat are you working with.
You can do a save as to get a WORD file, but do not expect great results. The ability to get a decent WORD file depends on what the form of PDF you are working from. If it was created from WORD with tags and all, you might get good results. If not, you might get a lot of messed up results.
Explain what you are starting with and your ultimate goal. Also check the audit of the file (should be under PDF Optimize) to see where the file information is concentrated (text, fonts, graphics, other).