Size depends to an extent how you produce a PDF. But there are many good reasons for distributing a document intended for reading (rather than editing) in PDF in my view. There are plenty of simple programs out there to produce a PDF these days, perhaps the easiest are those that create a PDF printer driver -
here is a selection.
You'll get the best reduction in file size for a Word doc containing graphics (this applies to most formats, in fact) but you will still get improvements with simple text contents. One of the main benefits that you might find useful from PDF is that the doc will be presented and laid out in the way that the originator intended.