This option is exclusive for documents generated in PDF, or else created with the Photoshop program.
Photoshop PDF Rendering Options
This option will manage Photoshop PDF files using Alpha channels. Here the Image resolution can be set and the rendering color space with or without overprint. Practical example you can fine in Inedit's help center.
PDF/Postscript Rendering Options
In this part you can configure PDF and Postscript default input. This option will make color conversions directly to the printer, allowing color substitution rules to take place. For more information about Rendering color space, refer to section 9.0 Preferences in this document.
Selecting DeviceN with Ink Limit control enables the curve control, the option to control the spot colors behaviour in PDF gradients in Black with a curve. Click on 'Edit…' to open the curve window.