In your previous post you asked how to use color fill for flat pattern How-to-color-a-flat-pattern. It would helpful to understand why you do this (see my question in linked post). Maybe 'fill' is not the correct method for your purpose?
Sorry i do not have NX9 (which i suppose you are working right now) but in NX11 it seems possible . Below is the setting i used for making annotations visible in an AREA FILL.
Here is the PDF exported out of it.
To make a Flat-Pattern sheet metal more visible also enlarging the outlines of the Flat-Pattern would help.
Now lines coming from bend annotations and dimensions are difficult to separate from the Flat-Pattern outlines.
I would recommend setting up your sheet metal and drafting template preferences to define the line widths for flat pattern views. Once set, the outlines should be clear and you then have no need for the extra step of color fill.
Sheet Metal Preferences-->Flat Pattern Display
Drafting Preferences-->View-->Flat Pattern
I hope this helps.
NX out-of-the-box, the defaults are 'Solid' Font and 'Normal' line width (Customer Defaults-->Sheet Metal-->Flat Pattern-->Curves)
The actual values for line widths are defined in Customer Defaults-->Line Widths.
If you created a Template for new files, these values will be stored there.
Setting up templates and defaults for each file type is totally configurable.