Saving Gmail mail items to PDF results in html type files

I want to save an actual email from Gmail as a off to Drive, directly from my mobile phone (lg g2). For example I may save a receipt from play store as a PDF.

However the resultant file turns out to be a rambling html type file. I use the print option from Gmail.

Saving an attachment works fines.

I can't locate any options or settings that may impact the printing process.

I would appreciate any advice from others who may have experienced this issue.

Thanks