Hi Aitlahmid,
Thank you for Contacting Syncfusion support.
We are unable to reproduce the reported issue with the provided details. Can you please share us the PDF document, details of the annotation in which you are adding in PDF Viewer, console error/exception details and the simple sample in which the issue could be reproduced . These details will be helpful for us to investigate further and assist you better.
Regards,
Akshaya