How to AirDrop PDF files between iPhones

I downloaded a PDF file which is 143 MB (probably relevant) to my iMac and AirDropped it to my iPhone, from there in iBooks I tried to AirDrop it to a friend’s iPhone but when I pressed the share button, the only option available was to print. I haven’t shared any other smaller PDF files so I don’t know if size is the issue, but how can I AirDrop this PDF file between iPhones? Preferably through iBooks.