Hi Manuel,
Thank you for using Syncfusion products.
We can create custom components/controls in the ASP.NET MVC application to call the APIs of the PDF viewer control. Please find the public methods, properties and events of the PDF viewer control in the following API documentation.
We have created a custom toolbar sample to demonstrate the same. You can download the sample from the following link.
In the above sample, we have updated the current zoom value using zoomChange event of the PDF viewer control in a text box control. The signatures can also be added to the PDF document using the addSignature() API of the PDF viewer control.
Please let us know that the above sample meets your requirements. If not, please let us know your requirements regarding the custom components. It will be helpful for us to analyze further and assist you better.
Regards,
Sabari Anand