Digital signatures

Digital signatures can be used in PDF documents to authenticate the identity of a user and the document’s contents. A signature stores information about the signer and the state of the document when it was signed. Acrobat users sign PDF documents in signature fields, which are a type of form field.

Signatures can have several types:

•	A certifying or author signature enables the author of a document to attest to its contents and specify the types of changes permitted for the document to remain certified. It must be the first signature in the document.

•	Regular or ordinary signatures enable signers to attest to the contents of a document but do not specify permitted changes. All signatures in a certified document other than the first one are ordinary signatures, as are all signatures in non-certified documents.

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Usage rights signatures are created when usage rights are added to a document by a product such as the Reader Extensions service. These rights enable users to perform operations in Adobe Reader, such as filling in form fields, that are not normally permitted. Usage rights signatures cannot be created by individual users.

You cannot create digital signatures using the Assembler service. However, when you assemble documents, some operations have an effect on digital signatures that are present in the source documents:

•	When specifying save="Full" for a PDF result document, all signatures become invalid and certifying signatures from non-base documents are removed. (See Saving PDF documents.)

•	Signatures become invalid when disassembling documents using the PDFsFromBookmarks element. (See Disassembling PDF documents.)

•	Signatures become invalid when flattening form fields using the NoForms element. (See Working with forms.)

Certification can only be retained for the result document if the base document is certified. Certification in non-base documents is never retained.

You can specify certification="None" on the result document to indicate that the result document should not be certified. If you do not specify the certification attribute, certification is retained for the result when the base document is certified, except in the following cases:

•	If you specify save="Full" or save="FastWebView", the result document is reorganized and therefore the certification becomes invalid.

•	If you specify the NoForms element, signature fields are flattened along with other form fields (see Working with forms). Therefore, the certifying signature will be removed.

You can remove usage rights from a document by specifying a value of None for the readerUsageRights attribute of the PDF result document.

Current page: http://livedocs.adobe.com/livecycle/es/sdkHelp/programmer/sdkHelp/assemblePDFSecurity.105.4.html