Use an Acrobat action command in the link.
These are examples of valid action commands for PDF documents linked from HTML:
<a href="http://www.adobe.com/prodlist.pdf#page=3" <a href="http://www.adobe.com/prodlist.pdf#namedest=Digital-Imaging" <a href="http://www.adobe.com/prodlist.pdf#zoom=200,250,100"You can put multiple action commands in a single URL command line if you separate the commands with an ampersand (&). Each command can be up to 32 characters in length. Be careful not to introduce any spaces in the line. For example,
<a href=http://www.adobe.com/prodlist.pdf#page=72&view=FitH,100> <a href=http://www.adobe.com/prodlist.pdf#pagemode=bookmarks&page=3>
There's info on setting a named destination into a PDF file at http://www.tinaja.com/linkpdf1.html and it seems that references then work without the namedest= part too.
The methods work on some browsers only, and this may depend on the interface between the browser and the PDF viewer. On IE, it seems to work, but not on Netscape 6 or Opera 6 (on which the #... part is effectively ignored).