In our fourth article on PDF security, we demonstrate how to certify and sign a PDF file. Certifying a document rather than signing it is useful if you want the user to make approved changes to a document.In our previous articles, you signed a PDF document to signify that you had approved the content. You can also certify the contents of a PDF document. Certifying a document rather than signing it is useful for users to be able to make approved changes to a document.
If you sign a document, and anyone (even you as the signer) makes changes, the signature is invalidated.
However, if you certify a document and a user makes approved changes, the certification is still valid. You can certify forms, for example, to guarantee that the content is valid when the user receives the form.
You, as the creator of the form, can specify what tasks the user can perform. For example, you can specify that readers can fill in the form fields without invalidating the document. However, if a user tries to add or remove a form field or a page, the certification will be invalidated.
Now you'll certify a form to be sent to clients of a winery, asking them to estimate their purchases. By certifying the form, you are sure that the client fills out the form as you designed it, with no additions or deletions to the form fields.
1. Open this PDF file and save it to your hard drive.
2. Choose File > Document Properties, and click the Security tab.
The information in the Document Properties dialog box shows that no security and no restrictions have been applied to the document.
3. Click Cancel to close the Document Properties dialog box without making any changes.
4. Choose File > Save As Certified Document.
5. Click OK to clear the message box. You'll use the digital ID that you created earlier in the lesson to certify the file.
6. From the Allowed Actions menu, choose Only Allow Commenting and Forms Fill-in Actions on This Document.
7. Leave the option checked that locks the certifying signature so that no one can modify or delete your certification. (The option is selected when a check mark is visible in the box.) Then click Next.
8. Click Next again to clear the warning box.
In the Select Visibility dialog box, if you choose the Show Certification on Document option, your signature will appear on the document alongside a blue ribbon certification. For this lesson, you'll choose not to show the certification on the form.
9. Select the Do Not Show Certification on Document option, and click Next.
10. If you have created more than one digital ID, select the digital ID to use, and click OK. We selected T. Simpson, Director.
11. Enter your password. We entered Lotion123.
12. Choose a reason for signing the document. We choose to certify that we attested to the accuracy and integrity of the document.
13. Click the Sign and Save button and complete the certification process.
14. Click OK to clear the message box.
15. Click the Signatures tab to review what actions the certification allows.
Next Page: Signing a certified document
Signing a certified document
Now you'll sign the document that you just certified to verify that filling in a signature field doesn't invalidate the certification.
1. Click the Sign button on the toolbar, and choose Sign This Document from the menu. Click OK to close the message box.
2. With the Hand tool selected, click in the signature box at the foot of the page.
3. In the dialog box, if you have more than one digital ID defined, select your digital ID, and then click OK. We selected T. Simpson, Director.
4. Enter your password. We entered Lotion123.
5. Select a reason for signing the document if you wish. Then click Sign and Save to complete the process. Click OK to clear the alert box.
6. Click the Signatures tab, and expand the certification entry marked with the blue ribbon icon.
Notice that the certification is still valid even though a signature has been added. If you had signed the document before you certified it and then added a comment, your signature would have been invalid.
7. Choose File > Close. You're done!
In our next security article, we'll look at your security settings and show you how to add passwords to a file.
Pages 356-359 excerpted from "Adobe Acrobat 7.0 Classroom in a Book." Copyright © 2005. Used with the permission of Pearson Education Inc. and Peachpit.
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