Hello - I am trying FMPA 14 for the 1st time today & had a PDF related Web Viewer issue as well - specifically a Base 64 issue on Mac running OS 10.10.3
Sometime in the last month or so I had the privilege of reading Mike Duncan's FileMaker 13: Working with Base 64 article, and I had some success with FMPA 13 learning from his example file.
However, today using FMPA 14 for the first time, I could not get part of his example file to work as it had for me in FMPA 13. The specific issue I've noticed occurs in the "Display in a Web Viewer" tab when the image file provided is a PDF.
In FMPA 13, the Web Viewer displayed a PDF, but with FMPA 14, what appears to be a loading bar shows up instead (and it stays like this indefinitely).
On a related note, I did upload the example file to FMS 14, and it works fine in WebDirect for me as well as when I open the file remotely via FMPA 13. Just not FMPA 14.
Prior to posting this, I contacted Mr. Duncan about this & he indicated it still seems to work for him in FM 14. I am wondering if you gave it a try what would happen. Perhaps this issue is only affecting a select portion of users & your discussion will enable someone to lead us to a solution.