I created a very simple SVG file with two text boxes using Inkscape.
Princexml 6+7 creates an empty PDF file (no contents shown).

A similar SVG file created using Adobe Illustrator is converted properly.

Bug or Feature?

Could you post here or email me (mikeday@yeslogic.com) the SVG file?

This SVG document places the text inside the <flowRoot>, <flowRegion>, and <flowPara> elements. These are not defined in SVG 1.0 or 1.1, which uses the <text> and <tspan> elements. I think these were added to a draft of SVG 1.2, which Inkscape implemented a little early. They have since been removed from the draft, and are not standard SVG.