When exporting a metrics view that has been set to an extended period of time such as 90 days, where the metric view shows data for the full 90 days, the PDF export does not.
DN data (daily average data) is not included in the PDF export.
Validate current data engine data retention information:
In the above image, 'Delete historic data older than' is set to 70 days, so the graph in the UI will pull from the DN table as well to show the entire timeframe. The PDF export excludes this.
This will be fixed in CU6.