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Adding another digital signature to pdf makes the old signature invalid.

I successfully manage to digitally sign pdf document using external hash. (https://www.syncfusion.com/forums/142454/how-to-add-signed-hash-to-pdf-as-signature)
but then if I try to add another signature to the document the old signature become invalid.
can you help with that?

Attachment: Outputsigned_31ce9f77.rar

5 Replies

SK Surya Kumar Syncfusion Team May 8, 2019 01:21 PM UTC

Hi Ahmad, 

Thank you for contacting Syncfusion support. 

We have created a sample for your requirement, please try the same and let us know if the provided solution work from your side. 

Note: The issue which you have mentioned may also occur if there is trial version watermark applied to every PDF which you have created. So please make sure you are using the licensed version assemblies and there is no watermark added to PDF 

Surya Kumar 

AH Ahmad May 9, 2019 08:42 AM UTC

Yes I still working on trial version of Syncfusion. And I don't add any watermark to pdf. do you? 
also will this be fixed after I moved to licensed version?

SL Sowmiya Loganathan Syncfusion Team May 9, 2019 11:20 AM UTC

Hi Ahmad, 

If you are using the trial version of Syncfusion, it will add watermark to every PDF document which you have created. So the reported issue “Signature becomes invalid” may occurs due to this. This issue will be fixed once you moved to licensed version. Please let us know if you have any concerns on this. 

Sowmiya L 

FH Fady Huwaidy April 11, 2022 10:29 PM UTC

Hi Syncfusion Team,

I have the same issue, I tried using the community license, but the trial watermark still there. Can I use the community license with the PDF library?



JM Jeyaseelan M Syncfusion Team April 12, 2022 12:41 PM UTC

Hi Fady,

Starting with 2022 Volume 1 v20.1.0.47, we are enforcing all Syncfusion customers (evaluators and paid customers) who use Syncfusion installers or NuGet packages from nuget.org must generate and register the corresponding platform and version license key in your projects.


Our license keys are version and platform-specific and it’s just a string that needs to be registered before initiating any Syncfusion controls in your application. So, please ensure that all the referenced Syncfusion assemblies\NuGet packages are on the same version as license key’s version.

Ensure that Syncfusion.Licensing.dll is referred in your project and the proper license key is registered in your application.  

Also, you should set “CopyLocal” to True to Syncfusion.Licensing.dll along with all other Syncfusion assemblies and ensure that the Syncfusion.Licensing.dll assembly also deployed with your application in same version

Find below the details to know about generating license key,


Find below the details to know about 
registering license key,


Find below the knowledge base article to know about which version license key should use in application,


Note: If you are using any template file for generating the PDF document, please ensure that the original template file doesn’t has any license trial warning.

Could you please follow below kb article to know more information on removing the license warning message?


If the reported issue is still not resolved,  please share us the following details to check issue from our side, 

  1. List of Syncfusion NuGet packages\assemblies used and its version.

  1. License key registered with faded line.

  1. TargetFrameWork and Platform of your application.

  1. Screenshot of the issue and license key registered place.

Issue occurring system date’s regional format. Please change the date’s regional format to English (United States) in the Server and confirm the application is working properly without any license errors?


Jeyaseelan M

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