Convert PDF to ODG

pdf to odg conversion looks like an attempt to recover OpenDocument graphics from PDF document, something that might perhaps be doable. You will have to use some dedicated PDF recovery tool for this and essentially try to recover the graphics to any vector based graphics, which can then be used to recreate the .odg file using OpenDocument based drawings tool which support ODG format.

Some online conversion services claim to support this as well, so it might be worth a shot, especially for some simple graphics.