Eric wants to be able to lock a PDF file so that nobody can modify it. Leo says that every PDF creator, including Adobe Acrobat, can protect it so it can't be modified. He can also also set the PDF so that the document cannot be forwarded to anyone else. If he trusts the person that he's sending it to, he can encrypt the PDF so it requires a password to open it. But understand that if they can open it, they can make an image of it and share it outside of that. So he'll need to trust the person he sends it to.
Kathy is trying to use a PDF form, but it's locked. How can she write to it and fill in the forms? Leo says there are products that can do it, but she can't do it with Adobe Reader. She'll need a program that can open and edit the PDF. Leo recommends FoxIt. It's free and she can use it to edit protected PDFs. She can then save it out with no problem.
Mark hates Adobe Reader and has removed it in favor of using FoxIt. Leo says rightfully so! But he's concerned about security in FoxIt. Leo says that FoxIt has different issues. But with everything coming off the internet, it's a heck of a challenge to protect against it. Bad guys have moved on from trying to hack the operating system and are now going after third party software like Adobe reader or FoxIt. But since FoxIt has a smaller "footprint" on the internet, it's less risky.