How do I attach a PDF from iBooks to an email?

How do I attach a PDF from my iBooks app on my iPad Pro to an email? I do not use the iOS Mail app. I use gmail and have the gmail app and google drive app installed on my iPad Pro running iOS 11.2.6. The only options I have available from iBooks while viewing a PDF are “AirDrop” and “Print”. While composing an email in the gmail app the attachment selection appears to only allow me to choose pictures and videos from my Photos app or items which are already stored on my google drive. I expected the iPad Pro to be much friendlier in working with PDFs. Any help or suggestions are greatly appreciated. Thank you!