Acrobat 9 gives you all the tools you need to sign a PDF document to indicate your approval or certify a PDF document to approve its contents. Acrobat also provides the tools you need to secure your PDF documents. You can use passwords to restrict users from opening, printing, and editing PDF documents. You can use a certificate to encrypt PDF documents so that only an approved list of users can open them. If you want to save security settings for later use, you can create a security policy that stores security settings. You can also permanently remove sensitive content from your PDF documents by using the Redaction feature.
In this exercise, you'll create a digital ID that uses an image, digitally sign documents, apply password protection to a file to restrict who can open it, apply a password to limit printing and changing of the file, and learn how to certify a document. (If you don't have the example files from the book, you can work with your own PDF documents.)
About Digital Signatures
A digital signature, like a conventional handwritten signature, identifies the person signing a document. Unlike a handwritten signature, however, a digital signature is difficult to forge because it contains encrypted information that is unique to the signer and easily verified.
To sign a document, you must obtain a digital ID from a third-party provider or create a self-signed digital ID for yourself in Acrobat. The digital ID contains a private key that is used to add the digital signature and a certificate that you share with those who need to validate your signature.
For information about Adobe security partners that offer third-party digital IDs and other security solutions, visit the Adobe website.