foreach (var item in tables)
{
    if (item.PreferredWidth.Type == Telerik.Windows.Documents.Flow.Model.Styles.TableWidthUnitType.Fixed && 
        item.PreferredWidth.Value == 0)
    {
        item.PreferredWidth = new Telerik.Windows.Documents.Flow.Model.Styles.TableWidthUnit(Telerik.Windows.Documents.Flow.Model.Styles.TableWidthUnitType.Percent, 100);
    } 
  
    
}

System.ArgumentOutOfRangeException: 'Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index'

<< /BaseFont /Arial /Encoding 21 0 R /Name /F13 /Subtype /Type1 /Type /Font >>

row.Height = new TableRowHeight(HeightType.Exact, image.Image.Height); 

<w:tblW w:w="11160" w:type="dxa"/>

<w:pgSz w:w="12240" w:h="15840"/>
<w:pgMar w:top="630" w:right="1440" w:bottom="540" w:left="1440" w:header="720" w:footer="720" w:gutter="0"/>

IEnumerable<Table> tables = document.EnumerateChildrenOfType<Table>();
foreach (Table table in tables)
{
	if (table.PreferredWidth.Type == TableWidthUnitType.Fixed)
	{
		table.PreferredWidth = new TableWidthUnit(TableWidthUnitType.Auto, table.PreferredWidth.Value);
	}
}