While browsing a local Church parish website recently, I noticed they had a link to their parish bulletin, in PDF format. I was perplexed, however, by the fact that there was more screen real estate taken up by text and a button that informed me I needed Adobe Acrobat to read the PDF than there was by the link to the bulletin itself!
How is Acrobat Reader as important as the links to the PDFs themselves? That's the message you send to the reader when he sees equal space given to Acrobat Reader instructions as the link(s) to the PDF(s) themselves.
The quick screenshot shown above is but the tip of the iceberg; Google "parish bulletin acrobat reader" for a ton of examples much, much worse than the one above. Instead of adding multiple lines of text, graphics, and buttons, the most I would put on any site (even for older audiences) is "Adobe Reader is required to view the PDF files above." Doing so conveys everything a user would need to know, and doesn't distract from the rest of the page. It also makes the page load faster (one less image to load).
The best thing to do, in my opinion, is to simply put PDF in parenthesis after the link to the file, like so:
Most people already have Adobe Reader on their computers, so it's redundant to tell them anything more. Telling them directly what the format of your file is (e.g. PDF, Word, Image) gives them more useful information than telling them what programs they'll need to use anyways. Mac users don't, in fact, need Adobe Reader—they already have Preview built into the system. Making them download additional software isn't a nice thing, now, is it?
So, for the future's sake, please don't add tons of irrelevant information to a site, unless the site's audience should be presumed to not know they need Adobe Reader or a similar program to view the file you're linking to.
(Better yet, why don't you post the bulletin in an online format, so they don't need any extra software to read it?).