@Pavani_Regulagedda 

Adding a button in view is not currently supported in Constellation. However, the requirement can be achieved using a link, which aligns with the recommended approach.

Please refer to the following community post: https://community.pega.com/conversations/user-experience/preview-pdf-in-constellation

In that, Method 2: Preview PDF on click of a link (Partial view) appears to be the most suitable solution for this use case.

Implementation Steps

1. Import the Constellation DX Component into your application.

2. Navigate to the DX Components tab under the Library.

3. Enable the Display PDF component.

4. Use this component in your view and configure it to open the PDF in a partial preview when the link is clicked.

For detailed steps on importing and enabling DX components, refer to the following guide: https://community.pega.com/conversations/user-experience/getting-started-with-the-constellation-dx-components-ui-gallery

Please let me know if this helps or if you need further clarification.