So I am having a lot of grief she it come too PDF in FileMaker containers.
Start with some facts:
Hosted on local network server
Mac OS (Yosemite, El Cap, and Sierra)
Container stored on External on Server
Field set as PDF on layout
Some users get a nice PDF image with a tool bar that allow them to open it up in full screen
Some users get a nice PDF image, but not tools bar
Some users get a not-nice PDF image. When they try to scroll or zoom is doesn't refresh properly and the image gets messed up.
Some user get NOTHING but a blank field.
Some users can load an image quickly
Some users get a spinning ball for a minute or more before it load.
I personally sat with two computers side by side. Both on same network. Both with same OS and and Acrobat ver. One was perfect, the other could not get a tool bar to appear and could not scroll the image.