1. From personal experience, PDFs are a lot easier on the eyes and printer and web friendly (not sure on their original purpose). I have made multiple applications for merchants to fill out pre-qual apps, contracts, etc. using Adobe Distiller. It looks a lot better than sending them a word document with lines to fill out on and they can fill them out on a webpage and print the pre-filled form and just sign their name.
2. On the toolbar, you can go to -> advanced -> security and choose from multiple features such as "encrypt with certificate" or "encrypt with password". As for not being able to send in an email, I can't possibly think of a way to block that other than blocking files being uploaded at all into your email accounts.
