There's no easy answer to your question and what you're posing. FYI, I'm in your industry and feel your pain. A few bits of advice. First, get over it and use the browser(s) that give you the best results. The most-specific reply is that both FF and Chrome now have built-in PDF viewers and Apple's Safari does not - in our field, Windows provides the best "compatibility" for PDF/TIFF or other take-off files - it's rare you'll find a Mac-friendly take-off file format. Since Adobe went "hands-off" with driving PDF compatibility earlier this year, you'll be hard pressed to find a single app or format that suits your needs - in other words, there aren't any more "can openers" any longer.
Apple's Safari uses Preview to generate "views" or "proxies", and Preview does not - by design - provide compatibility for all of what you'll find in PDF files (which I'm assuming that you're using) - the PDF viewer built into FF and Chrome gets updated far more often than Apple's Preview. Safari becomes more "powerful" if you install Adobe's Acrobat Reader or Acrobat CC (I own a license for the latter) and if you use Adobe's plug-in for the Reader or Acrobat CC app.
My advice? Do not waste your time trying to get Safari "working" for what you're looking for - I've been fighting that battle since 2007. It's not worth it, regardless of what file type you're looking to process. I have 25 Mac and 6 Windows workstations in my company - they all make coin; our estimating is done on 2 Windows workstations with specific software on it as our clients (agencies, owners, and generals) all are on Windows-specific software, and they've encoded their bidding documents in Windows-friendly portals - including the plan centers we work with.
I have a Parallels Desktop program on my Mac, with both Win 7 and Win 10 virtual machines - just to work with bid center documents and files. You've got to adapt to what the client is using, and Safari (or OS X, for that matter) isn't what they're using.