All returnable forms use a two-part encryption system: a separate encryption (with a separate key) for each page and an overall 128-bit encryption for the entire document. All free readers use a default encryption key. However, if the form's designer wants to create a form with a different key (password), he can. If the designer wants to distribute forms which become encrypted only after they are completed, he can do that also. The latter option is called the "Invoice Option" because it is ideal for customers who are completing order forms with credit card numbers or other personal information. If the document is intercepted, its doubly encrypted and thus basically worthless.

Returnable Forms are also secure in their content. They cannot accept external binary data, so they are not in a position to serve as a carrier for "Trojan Horse" types of programs.

Finally, Viri and worm programs thrive in systems which have event-driven scripting languages. Returnable Forms does not contain a scripting language. It does, however, contain a list of about 20 menu macro commands, all of which which are attached to the push-button. As a result, a Returnable Form cannot launch another program, or transfer malicious code when you open it. By design, the command set is limited strictly to matters internal to the form itself, and it does not use Visual Basic Script, which is responsible for the runaway majority of virus attacks.