<style>
    .no-open .k-blank-page {
        display: none;
    }

    /* Use these selectors if you want to separately target the upload or the dropzone */
    /* .no-open .k-external-dropzone,
    .no-open .k-upload{
        display: none;
    } */
</style>

<TelerikPdfViewer Data="@PdfSource"
                  OnOpen="@OnPdfOpen"
                  Height="600px"
                  Class="no-open">
    <PdfViewerToolBar>
        <PdfViewerToolBarDownloadTool />
        <PdfViewerToolBarPrintTool />

        <PdfViewerToolBarSpacer />

        <PdfViewerToolBarPagerTool />

        <PdfViewerToolBarSpacer />

        <PdfViewerToolBarZoomTool />
        <PdfViewerToolBarSelectionTool />
        <PdfViewerToolBarSearchTool />
        <PdfViewerToolBarAnnotationsTool />
    </PdfViewerToolBar>
</TelerikPdfViewer>

@code {
    private byte[] PdfSource { get; set; }

    private bool LoaderVisible { get; set; }

    private async Task OnPdfOpen(PdfViewerOpenEventArgs args)
    {
        // Cancel the event for additional precaution in case someone bypasses the CSS and forces the page to show the button and the dropzone.
        args.IsCancelled = true;
    }
}