Hi,
The answer to your main question is yes, do a search on google for filetype:doc or filetype:txt and you'll see tons of doc and txt files indexed.
The answer to your second question, if they offer any SEO, is a little more complex. You should try and see if you can get a page to be indexed if it is only linked from doc files.
Judging by my experience, I rarely see doc or txt files in the SERPs and even more rarely click on them if they show up. I'd rather do a HTML version of the page with a link to download the doc file in a directory blocked to spiders to avoid duplicates.
Best regards,
Guillaume Voyer.