Hi Rakesh,
Thank you for contacting Syncfusion support.
Query 1: Can we build non web based application for PDF making annotations using Syncfusion?
Essential PDF is a native .NET class library that non-web platforms (Windows, WPF, Xamarin etc.).
Query 2: My requirement is to take PDF file as input and then add annotations to the PDF file at the desired co-ordinates using API.
You can achieve your requirement by using the following UG link
Regards,
Prakash Kumar