I have seen this a few times now - if you import and try to Georeference a Vector PDF and the snapping to pixel locations in the image fail to work during the Georeferencing process, yet vector PDF snaps work once the image is georeferenced the issue is caused somehow by Bluebeam Revu - if you take a good PDF and break it up using Bluebeam, something changes in the PDF that throws TBC georeferencing process off so that the snapping fails until the image is georeferenced after which the PDF Vector Snapping works just fine.
This could be a Bluebeam defect or a TBC defect - I am trying to get a file over to Trimble so that they can take a look to see if there is anything that they are doing / not doing to cause the issue.
Alan