I found 6 associations for .psf:
.psf - ChiWriter - Outline PostScript printer font
.psf - MicroStation Plot specification file
.psf - ArcSoft PhotoStudio File image format
.psf - PowerSoft Report File
.psf - Insight II X-PLOR Molecular Structure File
.psf - Photoshop proof setup
It appears that Photoshop Proof Setup may be the correct one. Adobe help refers to it as a commercial printing format and says it can be opened with Adobe Illustrator. So, I checked whether my AI-CS3 could export or save as .psf and got nowhere. Same result with Photoshop CS3.
Sorry I couldn't help. If someone else doesn't solve it quickly, I will spend a bit more time on the Adobe site to see whether there is a plug-in I am missing.
John