An envelope is a container used to send one or more attached PDF files and/or other file types. The envelope panel provides a set of ready-to-use envelopes, along with tools to edit existing envelopes or create custom envelopes from a suitable image taken from one page of a PDF or image file. An explanatory text can be added to an envelope when you use it: do this with the typewriter tool or by placing a form field that accepts text.
Envelopes are usually used in connection with document security; choosing an envelope is the first of four steps in the Secure Delivery process. It is possible to use an envelope with no security linked to it, and it may contain a set of unsecured files. In these cases, the use of a portfolio provides a more flexible solution.
Envelopes can be covered by a security scheme and/or a signature scheme. Your security schemes are created stored and managed in the Security panel; your signatures in the Sign / Certify panel.
When creating an envelope, first choose an image. Then under Security Scheme, choose None, Privacy or No modification
Privacy means you set an Open Password each time you use the envelope.
No modification means you set a Permissions Password each time you use the envelope.
Under Signature Scheme you can choose any available signature scheme. Handwritten signatures cannot be used for signature schemes.
Your security applies to the envelope, not necessarily to the files inside it; PDF files in the envelope can have their own security, but other file types can usually not be password-protected, so applying security to the envelope protects those files as well.