Solder (see this for an example) has a melting point of 270C.
PET has a melting point of 250C.
If you could form 0.1mm cubes of each and arrange them in rows, then the "printing" process becomes a process of arranging row after row and layer upon layer into a finished (rectangular) shape - like a circuit board.
Subject the finished item to 240C and the solder and plastic will become soft enough to sinter to themselves while holding their relative shape.
The finished PCB won't be as tough as a regular PCB, but it would be possible to reuse them as they will separate with a sustained heat of 270C because of their different densities.
You obviously couldn't solder items to this PCB - they would need a mechanical contact to the solder.
Just make sure you have adequate ventilation!