Q: print to PDF on a Ipad Air 2?

In order to print from an iOS device requires a printer that is AirPrint capable, then you should have the option to print it. I don't believe it is possible to save it to your iPad as a pdf tho.

You ou can paste it into Pages and then save as a PDF.

Perhaps there  third party SW that can.

Use AirPrint to print from your iPhone, iPad, or iPod touch - Apple Support

I would recommend using PDF Converter by Readdle.

I dont know if you can just convert the email straight to PDF, but you could take a screen capture (touch home and power buttons at the same time) and then convert the photo to PDF.

This works for converting web pages to PDF and save it in iBooks. Not sure about emails. Check it out:

http://www.redmondpie.com/new-in-ios-9-save-as-pdf-lets-you-turn-any-content-typ e-to-pdf-format/