Signing multiple existing signature fields causes the error "Document has been altered or corrupted since it was signed"

[TRUONG BA HA]

Hi Team,

I tried to digitally sign a document with multiple signature fields in asp.net core and then opened it with Adobe Reader. I found that signing with Syncfusion modifies the document in some way and invalidates the previous signatures.

It's okay if you only use Syncfusion for the first signature and then use Adobe Reader to fill the next signature.

The same error was mentioned in the thread Sign multiple signatures in existing document - document has been altered  for winform

Thanks,

Best regards

[Gowthamraj Kumar]

Hi TRUONG, 

Thank you for contacting Syncfusion support. 

We can add multiple digital signatures in a PDF document by appending additional signatures to an already signed PDF file. We have checked the provided screenshot on our end, the document contains the trail watermark in it. When we add the signature for the first time without a license key, the trial watermark will be added and the document to be modified. So that, the second signature is Invalid. This is not an issue. To overcome this, we have to apply the register license key to avoid a trial watermark and get a valid signature.    

 

We have attached the sample with output document for your reference, kindly try the sample on your end and let us know the result. 

Sample: https://www.syncfusion.com/downloads/support/forum/168880/ze/NetCoreConsoleApp-1720229531 

Output: https://www.syncfusion.com/downloads/support/forum/168880/pd/Output1970269580

 

Screenshot: 

 

 

 

Please refer to this below link for getting the license key,  

KB: https://www.syncfusion.com/kb/8976/how-to-generate-license-key-for-essential-studio-products    

 

Please refer the below link for more information,   

KB: https://www.syncfusion.com/kb/9801/how-to-apply-one-or-more-digital-signatures-to-a-pdf-using-c-and-vb-net    

UG: https://help.syncfusion.com/file-formats/pdf/working-with-digitalsignature    

Blogs: https://www.syncfusion.com/blogs/post/create-validate-pdf-digital-signatures-csharp.aspx#add-multiple-digital-signatures-in-a-single-PDF-document    

  

Please let us know if you need any further assistance with this.   

 

Regards, 

Gowthamraj K 

[TRUONG BA HA]

Hi  Gowthamraj,

Yes, I was able to sign the document correctly several times after applying the correct license key.

Thanks a lot for your support and information.

Best regards,

Ha TB

[Gowthamraj Kumar]

Hi TRUONG, 

Thank you for your update. We are glad to know that your problem has been solved. 

Please let us know if you need any further assistance with this. 

Regards, 

Gowthamraj K