PROBLEM:
If you go to a softproof page in Firefox on Mac, the preview .PDF does not render inside the browser window. That's fine, Firefox Mac users know about PDF issues on Firefox.
Instead of rendering the .PDF, Firefox prompts the user if they wish to download the file, or the file gets auto-downloaded, depending on browser settings.
In either case, the file does not have a .PDF extension!!! It has a .PHP extension!!! End-users will be confused by this.
When the file finishes downloading, if you rename it to .PDF, it will then finally open in Acrobat. Myself I have no problem with this, but clients may have an issue, obviously.
This is generally a long-standing problem with Firefox (on Mac) in terms of handling PDF files.
SOLUTIONS:
-Make sure that when the file download happens, that it has a .PDF file extension instead of .PHP
-To make life easier for all visitors, regardless of browser software, it would be nice to have a hard URL link on the softproof page, so that people can manually grab the .PDF file if they have any problems.
-Ideally there should be a check if the user is on a certain browser, and instead of the .PDF preview in the page, they will see a message about having to download the .PDF manually.
In my testing (Win and Mac browsers) it's generally just Firefox on Mac that has issues. I believe Safari or Opera (one of the other, I forget which) on Mac may also have a rendering issue, but successfully downloads the file with a .PDF extension.