Word documents aren't PDFs.
You can use the File/Save As... option in the Toolbar to save a document in a variety of formats. (As long as what was pasted was actual text, and not page images from a PDF file on the web
).
What you may end up with is a text with the same layout as the web page (i.e. unwanted line breaks) that will look horrible on your eReader.
This thread describes different techinques to tidy up the layout.
Incidentally, this query may be more appropriate for the 'Workshop' forum rather than 'Which One Should I Buy'.