I know you've said that you don't want to make people use "secure software", but I think this is an application for an Adobe Acrobat document. You can prevent cut-and-paste, for example, and the Adobe Reader is so common now that most readers won't need to download it. (You don't need to buy anything - the "official" online converter is at
http://createpdf.adobe.com/ )
If your document is easily accessible on your site, readers won't need to send copies to anyone else, they can just send a link. You can hide the download URL behind a bit of JavaScript, so that there's no obvious direct link, so they need to come to your page and see the ads.
Whether they'll actually click on them is another story, of course. (I have never clicked on a website ad, because in the unlikely event it made it past the various ad blockers I've used over the years, it was never for anything I might want. These days I use NoScript to block all offsite scripts - those not on the site I'm viewing - by default, so I only see Google ads when I'm viewing a Google site.)