WhatsApp only allows you to share audio, video and images. No option to exchange documents, archives or otherwise using WhatsApp. However, making a slight detour, you can share files ZIP, RAR, APK, EXE, PDF, DOC, PPT, XLS etc. with your friends by WhatsApp.
I try other way to share pdf,but I find that my pdf is too large,then I try to compress my pdf.
I use a free software -- iMyMac PDF Compressor