DominoPDF supports all Windows 32-Bit and Windows 64-Bit operating systems.
If your Domino installation is running on another operating system (such as Solaris, Linux etc.) you can place a Windows machine in the same domain for DominoPDF usage.
As DominoPDF simply operates over HTTP you can place DominoPDF on a Windows server and access HTML content via HTTP on any other machine or operating system.
The benefits of using Domino on the Windows PC in your environment is the Linux Domino server can run the DominoPDF agent on the Windows Domino server. They can communicate and create/route the PDF accordingly.
DominoPDF will attempt to load HTML source via HTTP so as long as your Windows PC has access to your Domino servers on the Linux machines via HTTP you can convert.