To illustrate my question go to http://euler.slu.edu/teaching.html

Click on the link labelled "pdf format". The pdf document opens, in Reader 8
on my PC.

Now, with the pdf document still open, click on the link "pdf format" again.

I get a pop-up

File Download

Do you want to save this file?

Name: SuccessinMath.pdf
Type: Adobe Acrobat Document, 14.7KB
From: euler.slu.edu

Save    Cancel

The file you are downloading cannot be opened by the default program. It is
either corrupted or it has an incorrect file type. As a security precaution,
it is recommended that you cancel the download. How can I decide what
software to open?

When the pdf document is open and the user clicks on the link to the pdf
again, I want nothing to happen. Is there some way to achieve this? Maybe the
problem is with Reader 8, but I am not sure.

Cheers,
Ad Astra.