The Parallels Packer builder is able to create Parallels Desktop for Mac virtual machines and export them in the PVM format.
Packer actually comes with multiple builders able to create Parallels machines, depending on the strategy you want to use to build the image. Packer supports the following Parallels builders:
parallels-iso - Starts from an ISO file, creates a brand new Parallels VM, installs an OS, provisions software within the OS, then exports that machine to create an image. This is best for people who want to start from scratch.
parallels-pvm - This builder imports an existing PVM file, runs provisioners on top of that VM, and exports that machine to create an image. This is best if you have an existing Parallels VM export you want to use as the source. As an additional benefit, you can feed the artifact of this builder back into itself to iterate on a machine.
In addition to Parallels Desktop for Mac this requires the Parallels Virtualization SDK.
The SDK can be installed by downloading and following the instructions in the dmg.
Parallels Desktop for Mac 9 and later is supported, from PD 11 Pro or Business edition is required.