CMChinnu Muniyappan Syncfusion Team November 8, 2019 04:39 AM
Hi Hugo Minoodt,
Thank you for contacting Syncfusion support.
On our analysis with the provided output document, we found that the signature failure is due to adding the trial version watermark to the signed PDF document (“Created with a trial version of Syncfusion Essential PDF”). The issue will be resolved once adding a proper license key while signing a PDF document.
Starting with v16.2.0.x, if you reference Syncfusion assemblies from trial setup or from the NuGet feed, include a license key in your projects. Refer to the below link to learn about generating and registering Syncfusion license key in your application to use the components without trail message.