Hi Chris,
There's nothing in your link that contradicts my post. I gave no
disinformation although, I do accept that it may not have been a
complete answer.
I did think of expanding my response to include a note that many sites
include a link to a source of reader software that a site's visitor
could download and install, but it seemed to me that that didn't
answer what I understood to be the OP's principle query: how do I
control what happens when a user clicks a link to a PDF file.
The simple and only answer to that is that he can't!
Even if you follow your suggestion and include a link to some reader
software, it will still depend on the software installed, the options
available in that software and how they are set that will determine
whether the visitor gets the PDF file to open embedded within their
browser, open directly in that software's native window externally of
the browser, or some dialogue, such as the one the OP sees.
Rather than discouragement, my response was intended to be an
encouragement to seek more information on links to a variety of file
types other than HTML files, because the question itself indicated
limited understanding of what is possible within an HTML environment.