Hi Francois,
Thank you for contacting Syncfusion support.
We have tried to reproduce the reported issue with the provided details, but we were unable to reproduce the reported issue. We have shared the sample in which we have tried in the below link,
Also, our EJ2 PDF Viewer control is both server and client-side oriented. PDF viewer control processes the PDF document on the server-side(developed with the .NET environment) and sends the processed PDF data to the client using the web service to render the PDF document and for further operations in PDF viewer. So, there may be some delay in getting the response from the server due to network problems, hence the searched test takes some time to highlight in PDF Viewer. However, we can you please create the PDF Viewer web service project locally and provide that URL to the service URL of the PDF Viewer,
Please try it and revert us with more details, a PDF Document, and the modified sample, if any concerns about it.
Regards,
Akshaya