phranque - 8:42 pm on Jun 14, 2012 (gmt 0)

this isn't a browser/html issue - you need to fix this in the server response.
which HTTP Response headers are provided with the pdf file?
i would suggest that you need the following to meet your requirements:
Content-type:application/pdf
Content-length:[12345]
Content-disposition:attachment; filename=[foo.pdf]

[square brackets replaced with actual values]