What are "pk" Files?

I am using Audacity 2.0.0 on Microsoft Windows 7 Enterprise 6.1.7601 Service Pack 1 Build 7601.

I recorded several tracks using a Plantronics C610-M USB headset and exported them as “WAV (Microsoft) signed 16 bit PCM” files. I sent them to our editor to add to a PowerPoint presentation. The editor told me that I should have included the “.pk” files. What are the “.pk” files? When are they created? What did I do wrong?

“.pk” files have nothing to do with Audacity.
They are used in Adobe Audition Projects (formerly CoolEdit).

Are you sure that you set the WAV files and not the Audacity .AUP project file?