From in Activity Monitor, the memory usage of DTOCRHelper jumps from 1.2GB to 9.xGB in half a minute, after which the iMac will hardly react to keyboard and mouse.
The pdf is 78MB, so not sure it can be sent out by mail.
You could e.g. upload it to Dropbox and send a download link to cgrunenberg - at - devon-technologies.com - thanks!