Hi Thendy,
Thank you for using Syncfusion product.
We are unable to reproduce the issue. However, we have created a sample to convert the excel document to PDF document and the preview is loaded in the ejPdfViewer control. You can download the sample from the below link,
Can you please let us know how are you converting the excel document to PDF document and loading the PDF document to the ejPdfViewer control? Please modify the sample with your implementation to reproduce the issue. This will be helpful for us to analyze further in this and assist you better.
Please let us know if you need any further assistance.
Regards,
Sabari Anand