Encrypt files with password protection as part of the document mailing process

It should be possible to encrypt documents with a password bevor / when sending them.
In doing so, users should be able to choose whether to assign a password on a case-by-case basis, use a general password set up for all files, or, if necessary, assign a password according to a fixed pattern.

Example: Commission credit for business partners
The commission credit is posted in BC as a purchased invoice. The attachments include one or more files. The posted purchased invoice is assigned a document template and should be generated as a ZUGFeRD document. It should be possible to add these attachments as appendices within the PDF itself. Furthermore, it should be possible to attach additional files to the email via the appendices. The email attachments should be able to be encrypted with a password.
However, the file itself should not be encrypted in the appendices in BC but should be able to be opened normally.

Background: When purchase invoices are sent using the credit memo process, partners receive a commission credit note containing sensitive data. The Group requires that this information be protected with a password.