Greetings from Syncfusion.
We are unable to reproduce the issue “PdfViewerControl toolbar is not drawing icons” in our side. Kindly refer the sample in the below link which we used to reproduce the reported issue.
Please find the screenshot below for your reference,
Kindly share the following details to analyze more on this and assist you a better solution,
1. Simple sample to reproduce the issue.
2. Replication procedure to reproduce the issue
3. Syncfusion product version.
4. .Net Framework
5. Visual Studio version.
6. Operating System