PDF Preview functionality - how to disable?

I really wish we had the option to enable or disable the preview. I cannot stand it in certain situations. 

I'm a graphic designer at a sign shop, and often times I will use Dropbox to send proofs to my customers (when the files are too large to attach to an Email).

Often I WANT them to download the file, and not just preview it, so that they have it on their own personal computers.

Two example situations where I find it a problem:

1. I send a PDF with proof and pricing to a customer (expecting them to save it) but instead they just view it, then later down the road, when I'm cleaning out my dropbox, I delete it... then I get a phone call or Email saying:

"I can't find it now - the link doesn't work - I wanted to show my friend the layout"

MY DROPBOX ISN'T A STORAGE FACILITY FOR YOUR LOGOS OR LAYOUTS! I want them to download the file, so I can delete it after. I don't want to have to worry about having to hold on to old estimates and proofs for customers from months and months ago.

 2. I send a proof to a customer of some vehicle graphics (pin striping or a vehicle wrap) and I've designed it at full scale, when opened in the Dropbox preview, it opens it at 100% -- therefore, if my art board is the size of a truck cab, it comes in massive on screen. Not a huge problem because you would just zoom out, BUT:

(this is literally a true story) sometimes I deal with customers who are not tech savvy AT ALL (older business men/women) and I had a customer (who I sent some pin striping artwork to) and he could not figure out how to zoom out. When he viewed the PDF, he only saw a tiny portion of the vehicle graphics, and couldn't figure out how to see the whole thing; this would have been avoided if he was just FORCED to download the file in the first place, and not been able to preview it on Dropbox. Then it would have fit to screen on his computer. 

I've learned now to always send my proofs scaled down to 8.5" x 11" so that doesn't happen! but it is just annoying because now I have to take extra steps just in case I get another technologically impaired customer who doesn't understand how to zoom!

PLEASE GIVE US THE OPTION TO DISABLE PREVIEW!!!!!!