PDF Signature Panel Display

Question

What is the difference between the two pdf?

PDF_1

and

PDF_2

The first picture pdf signature is valid?

Answer 1

This information is copied from the book PDF and digital signatures:

Figure 2.17: Ordinary (approval) and Certification (author) signature

ISO-32000-1 specifies that a PDF document may contain the following standard types of signatures:

• One or more approval signatures— these signatures appear in signature form fields. The upper left document in figure 2.17 is an example of such a signature. Adobe Reader shows a green check mark when a valid approval signature is present.

• At most one certification signature— this signature can define different permissions, as shown in figure 2.17. You’ll see a blue ribbon when a document was certified.

• At most two usage rights signatures— these are signatures created using a private key that is proprietary for instance to Adobe. When a PDF document is signed with a usage rights signature using Adobe’s key, the document is Reader enabled. Adobe Reader will unlock certain usage rights, for instance allowing you to save a filled out form locally. Other vendors can use their private key to enforce similar usage rights. This type of signature is outside the scope of this paper.