Thank you for your post, and I apologize for the late reply.
I am unable to replicate the issue using Windows 10 Enterprise (64-bit). I launched FileMaker Pro Advanced 15.0.2, created a database file with a couple of Text fields, entered some data, and chose Save as PDF. The PDF was created, and I could open it under Microsoft Edge.
I then installed Adobe Acrobat Reader DC, and opened the PDF.
Back in FileMaker Pro Advanced 15.0.2, I saved as PDF again, and then opened in Adobe Acrobat Reader DC.
I updated to FileMaker Pro Advanced 15.0.3, opened the same file, saved to PDF, and the PDF opened in Adobe Acrobat Reader DC.
Since your workaround involved installing Acrobat Reader 11, try removing Acrobat Reader DC, and then reinstalling it again.
Keep me updated with any progress.