Did you set the field as "interactive" in layout mode?
Did you install Adobe Reader?
Have a quick search through this forum, this has been raised a number of times. From memory resolution has ranged from:
Install Adobe Reader
Don't install the DC version of Reader
As suggested by user 19752:
enter layout mode
select the field
Select the Inspector's data tab and scroll it to the very end.
Select optimize your container field for interactive content.
Return to browse mode
We've also seen this not available until after Reader has been launched and then after that launch FileMaker and the option appears.
Suggest searching on 'insert pdf'
Yes & yes.
When I made Adobe Acrobat Reader DC my PDF default instead of Adobe Reader Touch, I was able to insert PDF. Thanks!
Glad it is sorted John. There are a few hidden gremlins in the relationship between Filemaker and Reader within Windows!
Have a good weekend.