Digital signature and prevent subsequent changes

[vallegretti]

Hi,

i'm using Spire.pdf 5.3 to sign pdf documents.

I need to sign the document and prevent subsequent changes and subsequent signatures.

I'd tried setting the property "DocumentPermssion" of the object PdfSegnature to "ForbidChanges", but when i try to sign again the document no error was raised.

do you have any suggestion?

best regards

[Lisa.Li]

Hello,

Thank you for contacting.
Please kindly note that the purpose of the signature is to verify whether the document is valid and is modified or not. To prevent subsequent changes for the document, you need to protect the document by encrypting with password. Please refer to the tutorial (Encrypt and Decrypt PDF file) to achieve it. If there is any question, just feel free to write back.

Sincerely,
Lisa
E-icbelue support team