Whatsapp restricts the maximum size of the video by 64 MB (16 MB from Whatsapp web / 64 MB in case of Whatsapp web).
The art of exporting for Whatsapp is just getting the best export within the size limit of 64 MB
Step 1. Open FIle > Export > Media from Main menu of Adobe Premiere Pro.
Step 2: Under format, select H264 as the format.
H.264 offers good compression at lower file size and most modern mobile phones are able to play H.264 seamlessly.
Step 3. From preset, which is shown just below format, select