Rendering grid lines

GroupDocs.Viewer does not render grid lines of Spreadsheets by default. To enable rendering of grid lines you just need to set setRenderGridLines() property of HtmlViewOptions, JpgViewOptions, PngViewOptions or PdfViewOptions object to true in order to render the grid lines. 

The following code sample shows how to enable rendering of grid lines.

    try (Viewer viewer = new Viewer("sample.xlsx")) {
        HtmlViewOptions viewOptions = HtmlViewOptions.forEmbeddedResources();
        viewOptions.getSpreadsheetOptions().setRenderGridLines(true);
        viewer.view(viewOptions);
    }