FileMaker has long had a dependency on the client machine's OS to display PDFs, using Acrobat or Preview or whatever plugins/apps are on the local machine to show PDFs in Container fields.
As can be seen in various times and places over the years, this can create quite a mess due to unknown conditions on end-user machines (not all FM environments are tightly-controlled corporate environments), the mess that Adobe creates on some machines with multiple versions of Adobe Reader/Pro, etc, and other factors...and it's all completely unnecessary.
The PDF format has been totally open source for almost a decade, and it's pretty much a universally-used format, so FileMaker should just build in their own PDF functionality directly into the FM client, with no external dependencies. It's a core feature, just get it into the product. There are people in their garages on a weekend building open source PDF readers that do a great job, I'm sure that FMI devs can get that accomplished, and be done once and for all with all the mess involved with PDF-reading with FileMaker.
Same goes for PNG and JPG and other similar formats...not sure if the FM client is also using the local OS functionality to read those, but if it is, why bother: just build them in.