SUGGESTION: When opening a file on a Mac from within Acrobat or Reader have Acrobat or Reader permit the open file dialog box show both pdf files and fdf files.

Acrobat and Adobe Reader programmatically declare that the open file dialog box shows only PDF files, and all other formats, including FDF files, are greyed out. This requires the user to first click "Show: “All files” in order to access an FDF file, and for users who may do that frequently it is a pain. I can't think of a good reason to exclude FDF files from the open file process in Acrobat and Reader.