Check out example codes for "zoom inkcanvas". It will help you in understanding the concepts better.

Code Example 1

<ScrollViewer x:Name="scrollViewer" ZoomMode="Enabled" MinZoomFactor="1" VerticalScrollMode="Enabled" VerticalScrollBarVisibility="Auto" HorizontalScrollMode="Enabled" HorizontalScrollBarVisibility="Auto">
  <Grid x:Name="outputGrid" Background="{ThemeResource SystemControlBackgroundChromeWhiteBrush}" Height="Auto">
    <InkCanvas x:Name="inkCanvas"/>
  </Grid>
</ScrollViewer>

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