Check that the dashboard size is set to A4 landscape/portrait, as this will give the best experience. However, even if it is, there is a chance that this may not still be perfect, as Tableau is not designed to provide a pixel-perfect printed output. It's stength is being an online data visualisation tool for interaction online.
Thanks for your quick reply , i tried multiple ways to do that and your idea too but still facing the same issue.
As this is important for me to download the Dashboard and send it across.
Can you please help me our with possible way ?