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Sign multiple signatures in existing document - document has been altered


I created a document with 2 or more signature fields and then fill those fields with certificates with Syncfusion. Opening the signed document in Adobe Reader or using the new feature ValidateSignatures(..), only the last signed signature field is valid, and others produce error:

The document has been altered or corrupted since the signature was applied

Is it possible to sign document with multiple signatures without invalidating previous signatures? I tried to set the DocumentPermissions property on PdfSignature object to AllowComments or AllowFormFill and none of them solved my problem. I attached a simple project to this post to reproduce my problem.

Attachment: InvalidSignature_b8fd9898.zip

5 Replies

GK Gowthamraj Kumar Syncfusion Team January 17, 2020 10:26 AM UTC

Hi Daniel, 
Thank you for using Syncfusion product. 
Yes. We can add multiple signature in PDF document without invalidating previous signatures. For this, we have use the licensed packages for creation to resolve this invalidate signature issue.  
Note: Please make ensure whether you have using licensed assemblies. If you are using trial version, it will invalidate the older signature because of adding watermark to PDF.   
Please let us know if you need any further assistance on this. 
Gowthamraj K 

JP Joao Paulo Lima Braga February 10, 2020 07:08 PM UTC

Hi there,

I followed all the instructions here and in this reply, but no success. I am also getting the first signature invalidated after I apply the second signature. Any help on this problem? Thanks in advance.

Joao Paulo

SL Sowmiya Loganathan Syncfusion Team February 11, 2020 08:52 AM UTC

Hi Joao,  

We have analyzed the reported issue (first signature invalidated after apply the second one) and suspect that the issue may occurs due to using of trial assemblies (because of adding watermark). So please use the licensed assemblies to add the multiple signature in PDF document. 
Please find the below sample which illustrate the same from below,  

Output document screenshot:  
Please try the above sample in your end and let us know the result.  

Sowmiya Loganathan 

IT Itay October 17, 2020 05:02 PM UTC

I am not using trial assemblies (and no watermarks) yet get same result when signing 1 PDF with 2 signatures
Please check attached image and doc


Attachment: 2Signatures_c6032196.zip

SL Sowmiya Loganathan Syncfusion Team October 19, 2020 11:29 AM UTC

Hi Itay,   

We have created the sample to add multiple signature in the given PDF document (two signature in single PDF page) by adding two signature fields in it. Please find the download link for the same from below,   

Please try the above sample in your end and let us know if you have any concerns on this.   

Sowmiya Loganathan 

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