Adobe reader is updated from time to time. If one is using Adobe reader in vb.net or C## or other places, be aware that your software may not work any more unless you make necessary changes. Check out the version history here:
https://helpx.adobe.com/acrobat/release-note/release-notes-acrobat-reader.html
You may also check older versions of the software here:
https://www.adobe.com/devnet-docs/acrobatetk/tools/AppSec/protectedmode.html#faqs
Adobe reader protected mode is often makes it difficult for programmers to embed the adobe component with .net software. One most commonly encountered problem is that Protected Mode, which sand bags any third party pdf file initially. Check out more about the protected mode and other security options made available with recent Adobe Reader software:
https://www.adobe.com/devnet-docs/acrobatetk/tools/AppSec/protectedmode.html#faqs