Operation Manual

349

Electronic signatures

Last updated 4/7/2015

The required elements for establishing the validity of a signature include the signing certificate chain, certificate

revocation status, and possibly a timestamp. If the required elements are available and embedded during signing, the

signature can be validated requiring external resources for validation. Acrobat and Reader can embed the required

elements, if the elements are available. The PDF creator must enable usage rights for Reader users (File > Save As Other

> Reader Extended PDF).

Note: Embedding timestamp information requires an appropriately configured timestamp server. In addition, the signature

validation time must be set to Secure Time (Preferences > Security >Advanced Preferences > Verification tab). CDS

certificates can add verification information, such as revocation and timestamp into the document without requiring any

configuration from the signer. However, the signer must be online to fetch the appropriate information.

More Help topics

Validate a timestamp certificate

Configure a timestamp server

Set signing preferences

Add verification information at signing

1 Make sure that your computer can connect to the appropriate network resources.

2 Ensure that the preference Include Signature’s Revocation Status is still selected (Preferences > Signatures > Creation

& Appearances: More). This preference is selected by default.

3 Sign the PDF.

If all the elements of the certificate chain are available, the information is added to the PDF automatically. If a

timestamp server has been configured, the timestamp is also added.

Add verification information after signing

In some workflows, signature validation information is unavailable at signing, but can be obtained later. For example,

a company official may sign a contract using a laptop while traveling by air. The computer cannot communicate with

the Internet to obtain timestamping and revocation information to add to the signature. When Internet access is

available later, anyone who validates the signature can add this information to the PDF. All subsequent signature

validations can also use this information.

1 Ensure that your computer can connect to the appropriate network resources, and then right-click the signature in

the PDF.

2 Choose Add Verification Information.

Information and methods used to include this long term validation (LTV) information in the PDF comply with Part 4

of the ETSI 102 778 PDF Advanced Electronic Signatures (PAdES) standard. For more information, see

blogs.adobe.com/security/2009/09/eliminating_the_penone_step_at.html. The command is unavailable if the

signature is invalid, or is signed with a self-signed certificate. The command is also unavailable in case the verification

time equals the current time.